RFR: 8296653: ComboBox promptText is not displayed when the value is reset

Wed Nov 26 16:16:48 UTC 2025

The issue occurred because the skin marks the button cell as “empty” when the value becomes null.
With the fix clearing the ComboBox value re-shows the prompt text.
Tested using the code present in the bug.

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Commit messages:
 - Fix promptText is not displayed when the value is reset

Changes: https://git.openjdk.org/jfx/pull/1989/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1989&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296653
  Stats: 12 lines in 1 file changed: 12 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1989.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1989/head:pull/1989

PR: https://git.openjdk.org/jfx/pull/1989