RFR: 8371225: Missing release of GDK lock in Java_sun_awt_X11_GtkFileDialogPeer_run()

[Alexander Zvegintsev]

The `Java_sun_awt_X11_GtkFileDialogPeer_run` JNI function does not call `gdk_threads_leave` for the corresponding `gdk_threads_enter` in 3 cases of early return.
This simple change resolves the issue.

Testing looks good.

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Commit messages:
 - year
 - 8371225: Missing release of GDK lock in Java_sun_awt_X11_GtkFileDialogPeer_run()

Changes: https://git.openjdk.org/jdk/pull/28177/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28177&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371225
  Stats: 7 lines in 1 file changed: 4 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28177.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28177/head:pull/28177

PR: https://git.openjdk.org/jdk/pull/28177