[macos] NullPointerException originating from LWCToolkit.java

ADDITIONAL SYSTEM INFORMATION :
Mac OS Big Sur/Java 15

A DESCRIPTION OF THE PROBLEM :
With a complex Swing application running on Mac with Java 15, sometimes I find in the console this stack trace:

java.lang.NullPointerException: Null component provided to invokeAndWait
at java.base/java.util.Objects.requireNonNull(Objects.java:233)
at java.desktop/sun.lwawt.macosx.LWCToolkit.invokeAndWait(LWCToolkit.java:705)
at java.desktop/sun.lwawt.macosx.LWCToolkit.invokeAndWait(LWCToolkit.java:667)
at java.desktop/sun.lwawt.macosx.CAccessibility.invokeAndWait(CAccessibility.java:119)
at java.desktop/sun.lwawt.macosx.CAccessibility.getAccessibleComponent(CAccessibility.java:326)
at java.desktop/sun.lwawt.macosx.LWCToolkit.doAWTRunLoopImpl(Native Method)
at java.desktop/sun.lwawt.macosx.LWCToolkit.doAWTRunLoop(LWCToolkit.java:920)
at java.desktop/sun.lwawt.macosx.LWCToolkit.invokeAndWait(LWCToolkit.java:722)
at java.desktop/sun.lwawt.macosx.LWCToolkit.invokeAndWait(LWCToolkit.java:667)
at java.desktop/sun.lwawt.macosx.CAccessibility.invokeAndWait(CAccessibility.java:119)
at java.desktop/sun.lwawt.macosx.CAccessibility.getFocusOwner(CAccessibility.java:612)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Not sure, probably moving the keyboard focus between various components causes this.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I have not found a problem, it's just that the stack trace appears.
ACTUAL -
The stack trace should not appear.

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I'm afraid I do not have a sample source code to consistently reproduce this.
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FREQUENCY : rarely