Getting a theme for particular dpi failed in windows L&F during print test. Before [JDK-8294427](https://bugs.openjdk.org/browse/JDK-8294427) fix, theme was independent of DPI. After the fix (https://github.com/openjdk/jdk/commit/a63afa4aa62863d1a199a0fb7d2f56ff8fcd04fd) getting a theme in Windows L&F became dependent on DPI. Now it works fine in paint to a frame or window but for printing the DPI is computed with scaling factor which might not be w.r.t set of connected monitors and hence error is returned according to [this from windows document](https://learn.microsoft.com/en-us/windows/win32/api/uxtheme/nf-uxtheme-openthemedatafordpi). The suggested fix is to handle printer cases with default dpi since in error condition 0 is returned with `openThemeImpl(widget, dpi)`. The fix seems to be working fine without causing any regression (Tested in CI systems and also the affected tests).
------------- Commit messages: - Updated with null check - Fix Changes: https://git.openjdk.org/jdk/pull/18706/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18706&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8322135 Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/18706.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/18706/head:pull/18706 PR: https://git.openjdk.org/jdk/pull/18706
