DFG::ByteCodeParser needs to null check the result of presenceLike()

DFG::ByteCodeParser needs to null check the result of presenceLike()
https://bugs.webkit.org/show_bug.cgi?id=154135
rdar://problem/24291586

Reviewed by Geoffrey Garen.

ByteCodeParser::presenceLike() could return a null object property condition if it detects a
contradiction. That could happen due to bogus profiling. It's totally OK - we just need to
bail from using a property condition when that happens.

* bytecode/ObjectPropertyCondition.h:
(JSC::ObjectPropertyCondition::equivalence):
(JSC::ObjectPropertyCondition::operator bool):
(JSC::ObjectPropertyCondition::object):
(JSC::ObjectPropertyCondition::condition):
(JSC::ObjectPropertyCondition::operator!): Deleted.
* bytecode/PropertyCondition.h:
(JSC::PropertyCondition::equivalence):
(JSC::PropertyCondition::operator bool):
(JSC::PropertyCondition::kind):
(JSC::PropertyCondition::uid):
(JSC::PropertyCondition::operator!): Deleted.
* dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::check):
(JSC::DFG::ByteCodeParser::load):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@196446 268f45cc-cd09-0410-ab3c-d52691b4dbfc