Fix cypclass attr not initialized to NULL (breaks refcount)

Cython/Compiler/ModuleNode.py

@@ -920,6 +920,7 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
             constructor = None
             destructor = None
             for attr in scope.var_entries:
+                cname = attr.cname
                 if attr.type.is_cfunction and attr.type.is_static_method:
                     code.put("static ")
                 elif attr.name == "<init>":
@@ -930,7 +931,9 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
                 elif attr.type.is_cfunction:
                     code.put("virtual ")
                     has_virtual_methods = True
-                code.putln("%s;" % attr.type.declaration_code(attr.cname))
+                elif attr.type.is_cyp_class:
+                    cname = "%s = NULL" % cname
+                code.putln("%s;" % attr.type.declaration_code(cname))
             is_implementing = 'init_module' in code.globalstate.parts
 
             def generate_cpp_constructor_code(arg_decls, arg_names, is_implementing, py_attrs, constructor):