Unhandled Eventloop Exception (MacOS 14.3.1)

Windowbuilder was working with this window until the last batch of changes I made to it. I get no warnings or compile errors in my project, the Windowbuilder Design tap just show up empty.

My project is opensource and after doing some digging, the error appears in this (small) commit:
https://github.com/obscurestar/choordinates/commit/10c3ec90987c35c822aa5a1f17a3f8c548a0cc9e#diff-24bc5d99104ec827f095ecd47ae668ae04b178c150fd5750a9c31aa8502f89e9L136

and appears to be related to the creation of a new public constructor in the unrelated 'ToneChord' class. (Even with the removal of 'foo' object)

Below is the stack trace from the General Error log stack trace when I click the design tab for the 'Choordinates' window in my project.

java.lang.NullPointerException: String is null
at java.desktop/sun.java2d.SunGraphics2D.drawString(SunGraphics2D.java:2925)
at choordinates.FretPanel.paintComponent(FretPanel.java:273)
at java.desktop/javax.swing.JComponent.printComponent(JComponent.java:1292)
at java.desktop/javax.swing.JComponent.paint(JComponent.java:1132)
at java.desktop/javax.swing.JComponent.print(JComponent.java:1274)
at java.desktop/javax.swing.JComponent.paintChildren(JComponent.java:965)
at java.desktop/javax.swing.JComponent.printChildren(JComponent.java:1305)
at java.desktop/javax.swing.JComponent.paint(JComponent.java:1140)
at java.desktop/javax.swing.JComponent.print(JComponent.java:1274)
at java.desktop/javax.swing.JComponent.paintChildren(JComponent.java:965)
at java.desktop/javax.swing.JComponent.printChildren(JComponent.java:1305)
at java.desktop/javax.swing.JComponent.paint(JComponent.java:1140)
at java.desktop/javax.swing.JLayeredPane.paint(JLayeredPane.java:586)
at java.desktop/javax.swing.JComponent.print(JComponent.java:1274)
at java.desktop/javax.swing.JComponent.paintChildren(JComponent.java:965)
at java.desktop/javax.swing.JComponent.printChildren(JComponent.java:1305)
at java.desktop/javax.swing.JComponent.paint(JComponent.java:1140)
at java.desktop/javax.swing.JComponent.print(JComponent.java:1274)
at java.desktop/java.awt.GraphicsCallback$PrintCallback.run(GraphicsCallback.java:50)
at java.desktop/sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:75)
at java.desktop/sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:112)
at java.desktop/java.awt.Container.print(Container.java:2060)
at java.desktop/sun.lwawt.LWComponentPeer.print(LWComponentPeer.java:807)
at java.desktop/sun.lwawt.LWContainerPeer.print(LWContainerPeer.java:276)
at java.desktop/java.awt.GraphicsCallback$PeerPrintCallback.run(GraphicsCallback.java:103)
at java.desktop/sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:75)
at java.desktop/java.awt.Component.printAll(Component.java:3534)
at org.eclipse.wb.internal.swing.utils.SwingScreenshotMaker.makeShots(SwingScreenshotMaker.java:146)
at org.eclipse.wb.internal.swing.model.component.ComponentInfo.refresh_fetch(ComponentInfo.java:156)
at org.eclipse.wb.internal.swing.model.component.ComponentInfo.refresh_fetch(ComponentInfo.java:140)
at org.eclipse.wb.internal.swing.model.component.ContainerInfo.refresh_fetch(ContainerInfo.java:258)
at org.eclipse.wb.core.model.ObjectInfo.lambda$6(ObjectInfo.java:481)
at org.eclipse.wb.internal.core.utils.execution.ExecutionUtils.runDesignTime(ExecutionUtils.java:147)
at org.eclipse.wb.core.model.ObjectInfo.lambda$5(ObjectInfo.java:480)
at org.eclipse.wb.internal.swing.utils.SwingUtils$2.run(SwingUtils.java:78)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:773)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:720)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:714)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Reproduce the failure by opening the Choordinates window's WindowBuilder Design tab, then inspect FretPanel.java at line 273 and compare the behavior before and after the linked commit. Trace the null value reported by the drawString stack trace and determine why the new ToneChord constructor triggers it. Done means the design tab renders without the unhandled exception.

Written by the indexing model from the issue text.