Uncaught exception when adding group from cited references

From jabref created by [immoschott](https://github.com/immoschott): JabRef/jabref#10350

### JabRef version

5.10 (latest release)

### Operating system

macOS

### Details on version and operating system

_No response_

### Checked with the latest development build (copy version output from About dialog)

- [X] I made a backup of my libraries before testing the latest development version.
- [X] I have tested the latest development version and the problem persists

### Steps to reproduce the behaviour

1. Click "add group"
2. Under "Collect by" choose "Cited entries"
3. Select the aux file from an existing, successfully complied tex file with .bib references.

### Appendix


Detail information:

```
Opening: '/Users/username/Library/CloudStorage/Dropbox/library.bib'
Uncaught exception occurred in Thread[#50,JavaFX Application Thread,5,main]
java.lang.NullPointerException: Cannot invoke "org.jabref.model.util.FileUpdateMonitor.addListenerForFile(java.nio.file.Path, org.jabref.model.util.FileUpdateListener)" because "fileMonitor" is null
at org.jabref@5.10.60000/org.jabref.model.groups.TexGroup.create(TexGroup.java:51)
at org.jabref@5.10.60000/org.jabref.gui.groups.GroupDialogViewModel.resultConverter(GroupDialogViewModel.java:358)
at org.jabref.merged.module@5.10.60000/javafx.scene.control.Dialog.setResultAndClose(Dialog.java:1052)
at org.jabref.merged.module@5.10.60000/javafx.scene.control.DialogPane.lambda$createButton$3(DialogPane.java:795)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:232)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:189)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at org.jabref.merged.module@5.10.60000/javafx.event.Event.fireEvent(Event.java:198)
at org.jabref.merged.module@5.10.60000/javafx.scene.Node.fireEvent(Node.java:8944)
at org.jabref.merged.module@5.10.60000/javafx.scene.control.Button.fire(Button.java:203)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:207)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:232)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:189)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at org.jabref.merged.module@5.10.60000/javafx.event.Event.fireEvent(Event.java:198)
at org.jabref.merged.module@5.10.60000/javafx.scene.Scene$MouseHandler.process(Scene.java:3980)
at org.jabref.merged.module@5.10.60000/javafx.scene.Scene.processMouseEvent(Scene.java:1890)
at org.jabref.merged.module@5.10.60000/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2704)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:411)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:301)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:450)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:449)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.View.handleMouseEvent(View.java:551)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.View.notifyMouse(View.java:937)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.mac.MacView.notifyMouse(MacView.java:127)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.mac.MacApplication._enterNestedEventLoopImpl(Native Method)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.mac.MacApplication._enterNestedEventLoop(MacApplication.java:168)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.Application.enterNestedEventLoop(Application.java:515)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.EventLoop.enter(EventLoop.java:107)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:648)
at org.jabref.merged.module@5.10.60000/javafx.stage.Stage.showAndWait(Stage.java:469)
at org.jabref.merged.module@5.10.60000/javafx.scene.control.HeavyweightDialog.showAndWait(HeavyweightDialog.java:162)
at org.jabref.merged.module@5.10.60000/javafx.scene.control.Dialog.showAndWait(Dialog.java:345)
at org.jabref@5.10.60000/org.jabref.gui.JabRefDialogService.showCustomDialogAndWait(JabRefDialogService.java:268)
at org.jabref@5.10.60000/org.jabref.gui.groups.GroupTreeViewModel.lambda$addNewSubgroup$7(GroupTreeViewModel.java:161)
at java.base/java.util.Optional.ifPresent(Optional.java:178)
at org.jabref@5.10.60000/org.jabref.gui.groups.GroupTreeViewModel.addNewSubgroup(GroupTreeViewModel.java:160)
at org.jabref@5.10.60000/org.jabref.gui.groups.GroupTreeViewModel.addNewGroupToRoot(GroupTreeViewModel.java:124)
at org.jabref@5.10.60000/org.jabref.gui.groups.GroupTreeView.addNewGroup(GroupTreeView.java:516)
at org.jabref@5.10.60000/org.jabref.gui.groups.GroupTreeView.lambda$createNodes$0(GroupTreeView.java:158)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:232)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:189)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at org.jabref.merged.module@5.10.60000/javafx.event.Event.fireEvent(Event.java:198)
at org.jabref.merged.module@5.10.60000/javafx.scene.Node.fireEvent(Node.java:8944)
at org.jabref.merged.module@5.10.60000/javafx.scene.control.Button.fire(Button.java:203)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:207)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:232)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:189)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at org.jabref.merged.module@5.10.60000/javafx.event.Event.fireEvent(Event.java:198)
at org.jabref.merged.module@5.10.60000/javafx.scene.Scene$MouseHandler.process(Scene.java:3980)
at org.jabref.merged.module@5.10.60000/javafx.scene.Scene.processMouseEvent(Scene.java:1890)
at org.jabref.merged.module@5.10.60000/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2704)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:411)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:301)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:450)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
at org.jabref.merged.module@5.10.60000/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:449)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.View.handleMouseEvent(View.java:551)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.View.notifyMouse(View.java:937)
at org.jabref.merged.module@5.10.60000/com.sun.glass.ui.mac.MacView.notifyMouse(MacView.java:127)

```

Start with the stack trace in org.jabref.model.groups.TexGroup.create at TexGroup.java:51, then inspect GroupDialogViewModel.java:358 to follow how the cited-entries group is created. Reproduce the macOS workflow with an aux file from a compiled TeX file; done means adding the group no longer raises the reported NullPointerException.

Written by the indexing model from the issue text.