The reordering tests in TabPaneDragPolicyTest fail only fails on Mac. It may be a a product issue which is tracked by [JDK-8213136](https://bugs.openjdk.java.net/browse/JDK-8213136). This PR disables the 4 reordering test on Mac platform. And fixes an Exception, Please check the JBS for exception.
------------- Commit messages: - 8245601: [TESTBUG] Disable TabPaneDragPolicyTest on Mac until JDK-8213136 is fixed and fix ISE Changes: https://git.openjdk.java.net/jfx/pull/234/files Webrev: https://webrevs.openjdk.java.net/jfx/234/webrev.00 Issue: https://bugs.openjdk.java.net/browse/JDK-8245601 Stats: 13 lines in 1 file changed: 11 ins; 0 del; 2 mod Patch: https://git.openjdk.java.net/jfx/pull/234.diff Fetch: git fetch https://git.openjdk.java.net/jfx pull/234/head:pull/234 PR: https://git.openjdk.java.net/jfx/pull/234
