Merge pull request #23969 from asmorkalov:as/python2_test_fix

Fixed tests execution with Python 2.7

modules/python/src2/cv2_util.hpp

@@ -71,7 +71,7 @@ public:
     }
 
     operator bool() {
-        return static_cast<bool>(obj_);
+        return obj_ != nullptr;
     }
 
     PyObject* release()