java.lang.AssertionError GsfCompletionProvider.java

### Apache NetBeans version

Apache NetBeans 28

### What happened

Message from the notification system:
```

java.lang.AssertionError
at com.sun.tools.javac.util.Assert.error(Assert.java:155)
at com.sun.tools.javac.util.Assert.checkNonNull(Assert.java:62)
at com.sun.tools.javac.comp.Modules.allModules(Modules.java:1237)
at com.sun.tools.javac.model.JavacElements.getAllModuleElements(JavacElements.java:132)
at org.netbeans.modules.java.source.ElementUtils.getTypeElementByBinaryName(ElementUtils.java:48)
at org.netbeans.api.java.source.ElementHandle.getTypeElementByBinaryName(ElementHandle.java:705)
at org.netbeans.api.java.source.ElementHandle.resolveImpl(ElementHandle.java:179)
at org.netbeans.api.java.source.ElementHandle.resolve(ElementHandle.java:133)
at org.netbeans.modules.web.el.completion.ELJavaCompletionItem$ElementHandleAdapter$1.run(ELJavaCompletionItem.java:315)
at org.netbeans.modules.web.el.completion.ELJavaCompletionItem$ElementHandleAdapter$1.run(ELJavaCompletionItem.java:311)
at org.netbeans.modules.java.source.parsing.MimeTask.run(MimeTask.java:60)
at org.netbeans.modules.parsing.impl.TaskProcessor.callUserTask(TaskProcessor.java:586)
at org.netbeans.modules.parsing.api.ParserManager$MimeTaskAction.run(ParserManager.java:445)
at org.netbeans.modules.parsing.api.ParserManager$MimeTaskAction.run(ParserManager.java:428)
at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:181)
at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:178)
at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:153)
at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:335)
at org.netbeans.modules.parsing.nb.DataObjectEnvFactory.runPriorityIO(DataObjectEnvFactory.java:118)
at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:67)
at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:178)
at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:399)
at org.netbeans.api.java.source.JavaSource.runUserActionTaskImpl(JavaSource.java:433)
at org.netbeans.api.java.source.JavaSource.runUserActionTask(JavaSource.java:425)
at org.netbeans.modules.web.el.completion.ELJavaCompletionItem$ElementHandleAdapter.document(ELJavaCompletionItem.java:311)
at org.netbeans.modules.web.el.completion.ELCodeCompletionHandler.documentElement(ELCodeCompletionHandler.java:739)
at org.netbeans.modules.csl.editor.completion.GsfCompletionDoc.(GsfCompletionDoc.java:91)
at org.netbeans.modules.csl.editor.completion.GsfCompletionDoc.create(GsfCompletionDoc.java:108)
at org.netbeans.modules.csl.editor.completion.GsfCompletionProvider$JavaCompletionQuery.resolveDocumentation(GsfCompletionProvider.java:528)
at org.netbeans.modules.csl.editor.completion.GsfCompletionProvider$JavaCompletionQuery$1.run(GsfCompletionProvider.java:315)
at org.netbeans.modules.parsing.impl.TaskProcessor.callUserTask(TaskProcessor.java:586)
at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:197)
at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:180)
at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:181)
at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:178)
at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:153)
at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:335)
at org.netbeans.modules.parsing.nb.DataObjectEnvFactory.runPriorityIO(DataObjectEnvFactory.java:118)
at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:67)
at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:178)
at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:83)
at org.netbeans.modules.csl.editor.completion.GsfCompletionProvider$JavaCompletionQuery.query(GsfCompletionProvider.java:320)
at org.netbeans.spi.editor.completion.support.AsyncCompletionTask.run(AsyncCompletionTask.java:198)
at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1403)
at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:45)
at org.openide.util.lookup.Lookups.executeWith(Lookups.java:287)
[catch] at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2018)

```

### Language / Project Type / NetBeans Component

_No response_

### How to reproduce

Don't know.

### Did this work correctly in an earlier version?

No / Don't know

### Operating System

Win11

### JDK

OpenJDK21

### Apache NetBeans packaging

Community provided installer

### Anything else

_No response_

### Are you willing to submit a pull request?

No

Start with GsfCompletionProvider.java, especially JavaCompletionQuery.resolveDocumentation, and follow the stack through ELJavaCompletionItem.java and ElementHandle.java. Try to reproduce the assertion during completion documentation on the reported Windows 11 and OpenJDK 21 setup; done means the completion action no longer produces this assertion.

Written by the indexing model from the issue text.