RFR(S) 8194984: 9 Null pointer dereference defect groups related to ciMethodData::bci_to_data()

[dean.long at oracle.com]

http://cr.openjdk.java.net/~dlong/8194984/webrev/

https://bugs.openjdk.java.net/browse/JDK-8194984


Check for null value returned by bci_to_data().  I also removed some 
dead code I found in c1_GraphBuilder.cpp.


dl