[MO] Avoid maskedconstant to array conversion (#10233)

* Avoid maskedconstant to array conversion

* remove redundant input

* Add link to github issue

tools/mo/openvino/tools/mo/ops/ReduceOps.py

@@ -36,6 +36,10 @@ def reduce_helper(func: callable, x: np.array, axis: tuple, keepdims: bool):
     :return: the result tensor
     """
     result = func(x, axis=axis, keepdims=keepdims)
+    # we need to handle this case specially to avoid problems with deepcopy method with MaskedConstant converted to
+    # masked_array - see issue https://github.com/numpy/numpy/issues/21022
+    if isinstance(result, np.ma.core.MaskedConstant):
+        return np.ma.masked_array(data=-1, mask=True, dtype=result.dtype)
     if is_fully_defined(x):
         return result
     else: