RFR: 8344372: Setting width for TRANSPARENT Stage -> gtk_window_resize: assertion 'height > 0'

[Thiago Milczarek Sayao]

The bug happened when setting only width or height (not both) on a Stage that was oriented by the view size.

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Commit messages:
 - Fix 8344372

Changes: https://git.openjdk.org/jfx/pull/1654/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1654&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344372
  Stats: 118 lines in 2 files changed: 118 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1654.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1654/head:pull/1654

PR: https://git.openjdk.org/jfx/pull/1654