Invalid stack frame errors on variable hover

I have a breakpoint at:

```
"ForkJoinPool.commonPool-worker-9" #81 [469806] daemon prio=5 os_prio=0 cpu=14127.62ms elapsed=107.57s tid=0x00007f4954003b60 nid=469806 at breakpoint [0x00007f49cd36a000]
java.lang.Thread.State: RUNNABLE
at org.eclipse.jdt.internal.core.index.DiskIndex.addQueryResult(DiskIndex.java:161)
at org.eclipse.jdt.internal.core.index.DiskIndex.addQueryResults(DiskIndex.java:254)
at org.eclipse.jdt.internal.core.index.Index.query(Index.java:173)
at org.eclipse.jdt.internal.core.search.matching.TypeDeclarationPattern.queryIn(TypeDeclarationPattern.java:353)
at org.eclipse.jdt.core.search.SearchPattern.findIndexMatches(SearchPattern.java:2516)
at org.eclipse.jdt.core.search.SearchPattern.findIndexMatches(SearchPattern.java:2488)
at org.eclipse.jdt.internal.core.search.matching.MatchLocator.findIndexMatches(MatchLocator.java:294)
at org.eclipse.jdt.internal.core.search.PatternSearchJob.search(PatternSearchJob.java:237)
at org.eclipse.jdt.internal.core.search.PatternSearchJob.search(PatternSearchJob.java:212)
at org.eclipse.jdt.internal.core.search.PatternSearchJob.lambda$0(PatternSearchJob.java:148)
at org.eclipse.jdt.internal.core.search.PatternSearchJob$$Lambda/0x00007f4a94b24720.call(Unknown Source)
at java.util.concurrent.ForkJoinTask$AdaptedCallable.exec(java.base@21.0.10/ForkJoinTask.java:1456)
at java.util.concurrent.ForkJoinTask.doExec(java.base@21.0.10/ForkJoinTask.java:387)
at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(java.base@21.0.10/ForkJoinPool.java:1312)
at java.util.concurrent.ForkJoinPool.scan(java.base@21.0.10/ForkJoinPool.java:1843)
at java.util.concurrent.ForkJoinPool.runWorker(java.base@21.0.10/ForkJoinPool.java:1808)
at java.util.concurrent.ForkJoinWorkerThread.run(java.base@21.0.10/ForkJoinWorkerThread.java:188)
```

I then hover over `wordsToDocNumbers` in this code:

```
if (wordsToDocNumbers != null) {
```

This produces a logged error:

```
eclipse.buildId=4.39.0.20260305-0817
java.version=21.0.10
java.vendor=Arch Linux
BootLoader constants: OS=linux, ARCH=x86_64, WS=gtk, NL=en_US
Framework arguments: -product org.eclipse.epp.package.committers.product
Command-line arguments: -os linux -ws gtk -arch x86_64 -product org.eclipse.epp.package.committers.product -data /data/workspaces/xtext_tests -data file:/data/workspaces/xtext_tests/

org.eclipse.jdt.debug
Error
Wed Mar 18 22:21:56 EET 2026
Invalid stack frame

java.lang.IllegalStateException
at org.eclipse.jdt.internal.debug.core.model.JDIStackFrame.getUnderlyingStackFrame(JDIStackFrame.java:1381)
at org.eclipse.jdt.internal.debug.core.model.JDIStackFrame.getUnderlyingThisObject(JDIStackFrame.java:1013)
at org.eclipse.jdt.internal.debug.core.model.JDIStackFrame.updateVariables(JDIStackFrame.java:729)
at org.eclipse.jdt.internal.debug.core.model.JDIStackFrame.getVariables0(JDIStackFrame.java:397)
at org.eclipse.jdt.internal.debug.core.model.JDIStackFrame.getVariables(JDIStackFrame.java:308)
at org.eclipse.jdt.internal.debug.ui.JavaDebugHover.containsVariable(JavaDebugHover.java:620)
at org.eclipse.jdt.internal.debug.ui.JavaDebugHover.lambda$2(JavaDebugHover.java:639)
at org.eclipse.jdt.internal.debug.ui.JavaDebugHover.findFirstFrameForVariable(JavaDebugHover.java:604)
at org.eclipse.jdt.internal.debug.ui.JavaDebugHover.getHoverInfo2(JavaDebugHover.java:469)
at org.eclipse.jdt.internal.ui.text.java.hover.BestMatchHover.getHoverInfo2(BestMatchHover.java:165)
at org.eclipse.jdt.internal.ui.text.java.hover.BestMatchHover.getHoverInfo2(BestMatchHover.java:131)
at org.eclipse.jdt.internal.ui.text.java.hover.JavaEditorTextHoverProxy.getHoverInfo2(JavaEditorTextHoverProxy.java:89)
at org.eclipse.jface.text.TextViewerHoverManager$1.run(TextViewerHoverManager.java:155)
```

https://github.com/user-attachments/assets/eb789ce7-a037-4598-b6fb-5ccf1f433a4e