Editor deadlock and null pointer exception while parsing java file

### Apache NetBeans version

Apache NetBeans 13

### What happened

Pressing ctrl-space for suggestions leaves the editor in a freezing state.

Stacktrace reveals that in case the java source cannot be parsed, then the basedocument "loses" the write lock.

### How to reproduce

I pressed ctrl-space in the attached source file.

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

No

### Operating System

Linux

### JDK

11.0.15+10-Ubuntu-0ubuntu0.20.04.1

### Apache NetBeans packaging

Apache NetBeans binary zip

### Anything else

Reproduced 3 times in a row.

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

No

### Code of Conduct

Yes

Start by inspecting the attached Java source file and the reported stacktrace, then reproduce the freeze by pressing Ctrl-Space in the NetBeans editor. Trace the Java parsing path and BaseDocument write-lock handling; done means the editor no longer freezes or reports the null pointer exception when parsing fails.

Written by the indexing model from the issue text.