[9] Review Request: 8068275 Some tests failed after JDK-8063104

[Sergey Bylokhov]

Hello.
Please review a small fix for jdk 9.
The problem is in the Util.waitForIdle(Robot) which does not take into 
account that robot can be null.

Bug: https://bugs.openjdk.java.net/browse/JDK-8068275
Webrev can be found at: http://cr.openjdk.java.net/~serb/8068275/webrev.01

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Best regards, Sergey.