[10] RFR(XS) 8194982: 2 Null pointer dereference defect groups related to ProjNode::is_uncommon_trap_if_pattern()

[dean.long at oracle.com]

http://cr.openjdk.java.net/~dlong/8194982/webrev/

https://bugs.openjdk.java.net/browse/JDK-8194982

Static analyzer did not realize proj->is_uncommon_trap_if_pattern() in 
"if" prevents "unc" from being NULL, so rewrote code to assign result to 
local variable instead of calling is_uncommon_trap_if_pattern() twice.
Added assert for "dom_unc".

dl