RFR(XS): 8145328: SEGV in DirectivesStack::getMatchingDirective

[Nils Eliasson]

Hi,

Please review this fix of getMatchingDirective when running with JVMCI.

This also fixes JDK-8145331 that will be closed as a dupe as soon as 
this fix is in.

Testing:
All tests that failed passes now.

Bug: https://bugs.openjdk.java.net/browse/JDK-8145328
Webrev: http://cr.openjdk.java.net/~neliasso/8145328/webrev.01/

Regards,
Nils Eliasson