python: Fix check for disasm creation failure

Check should be for pointer being NULL, not what it points to.

Also adds a test for this case.

Reviewed By: indygreg

Differential Revision: http://llvm-reviews.chandlerc.com/D1878



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194965 91177308-0d34-0410-b5e6-96231b3b80d8

bindings/python/llvm/disassembler.py

@@ -75,7 +75,7 @@ class Disassembler(LLVMObject):
 
         ptr = lib.LLVMCreateDisasm(c_char_p(triple), c_void_p(None), c_int(0),
                 callbacks['op_info'](0), callbacks['symbol_lookup'](0))
-        if not ptr.contents:
+        if not ptr:
             raise Exception('Could not obtain disassembler for triple: %s' %
                             triple)