RFR: 8068293: [TEST_BUG] Test closed/com/sun/java/swing/plaf/motif/InternalFrame/4150591/bug4150591.java fails with GTKLookAndFeel

[Prasanta Sadhukhan]

Test fails in GTKLookAndFeel with NPE

java.lang.NullPointerException
at javax.swing.border.BevelBorder.<init>(BevelBorder.java:78)
at javax.swing.BorderFactory.createBevelBorder(BorderFactory.java:155)
at com.sun.java.swing.plaf.motif.MotifInternalFrameTitlePane$Title.<init>(MotifInternalFrameTitlePane.java:325) 

because `BorderFactory.createBevelBorder` tries to use brighter shade of highlight and shadow color which it tries to obtain from 
`UIManager.getColor("activeCaptionBorder")` and `UIManager.getColor("inactiveCaptionBorder")` both of which are not defined in GTK L&F as caption border are not used there

Fix is made to not use these color to create BevelBorder if these colors are not present..

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Commit messages:
 - 8068293: [TEST_BUG] Test closed/com/sun/java/swing/plaf/motif/InternalFrame/4150591/bug4150591.java fails with GTKLookAndFeel

Changes: https://git.openjdk.org/jdk/pull/27839/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27839&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8068293
  Stats: 7 lines in 2 files changed: 3 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/27839.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27839/head:pull/27839

PR: https://git.openjdk.org/jdk/pull/27839