Don't patch QPyNullVariant if it doesn't exist

Author: NathanW2

python/__init__.py

@@ -23,14 +23,17 @@
 # This will get replaced with a git SHA1 when you do a git archive
 __revision__ = '$Format:%H$'
 
-from PyQt4.QtCore import QPyNullVariant
-from types import MethodType
+try:
+	# Add a __nonzero__ method onto QPyNullVariant so we can check for null values easier.
+	#   >>> value = QPyNullVariant("int")
+	#   >>> if value:
+	#   >>>	  print "Not a null value"
+	from types import MethodType
+    from PyQt4.QtCore import QPyNullVariant 
+    def __nonzero__(self):
+        return False
 
-# Add a __nonzero__ method onto QPyNullVariant so we can check for null values easier.
-#   >>> value = QPyNullVariant("int")
-#   >>> if value:
-#   >>>	  print "Not a null value"
-def __nonzero__(self):
-    return False
+    QPyNullVariant.__nonzero__ = MethodType(__nonzero__, None, QPyNullVariant)
+except ImportError:
+    pass
 
-QPyNullVariant.__nonzero__ = MethodType(__nonzero__, None, QPyNullVariant)