Fix: incorrect handling of 3x3 matrices with RNA get/set callbacks

Thanks to @mont29 for spotting the error.

tests/python/bl_pyapi_prop_array.py

@@ -49,6 +49,19 @@ def seq_items_as_dims(data):
     return ((len(data),) + seq_items_as_dims(data[0])) if hasattr(data, "__len__") else ()
 
 
+def matrix_with_repeating_digits(dims_x, dims_y):
+    """
+    Create an array with easily identifier able unique elements:
+    When: dims_x=4, dims_y=3 results in:
+       ((1, 2, 3, 4), (11, 22, 33, 44), (111, 222, 333, 444))
+    """
+    prev = (0,) * dims_x
+    return tuple([
+        (prev := tuple(((10 ** yi) * xi) + prev[i] for i, xi in enumerate(range(1, dims_x + 1))))
+        for yi in range(dims_y)
+    ])
+
+
 # -----------------------------------------------------------------------------
 # Tests
 
@@ -463,20 +476,20 @@ class TestPropArrayMultiDimensional(unittest.TestCase):
                 self.assertEqual(data_as_tuple, data_native)
                 del id_type.temp
 
-    def test_matrix(self):
-        data = ((1, 2, 3, 4), (11, 22, 33, 44), (111, 222, 333, 444), (1111, 2222, 3333, 4444),)
+    def _test_matrix(self, dim_x, dim_y):
+        data = matrix_with_repeating_digits(dim_x, dim_y)
         data_native = seq_items_xform(data, lambda v: float(v))
-        id_type.temp = FloatVectorProperty(size=(4, 4), subtype='MATRIX', default=data_native)
+        id_type.temp = FloatVectorProperty(size=(dim_x, dim_y), subtype='MATRIX', default=data_native)
         data_as_tuple = seq_items_as_tuple(id_inst.temp)
         self.assertEqual(data_as_tuple, data_native)
         del id_type.temp
 
-    def test_matrix_with_callbacks(self):
+    def _test_matrix_with_callbacks(self, dim_x, dim_y):
         # """
         # Internally matrices have rows/columns swapped,
         # This test ensures this is being done properly.
         # """
-        data = ((1, 2, 3, 4), (11, 22, 33, 44), (111, 222, 333, 444), (1111, 2222, 3333, 4444),)
+        data = matrix_with_repeating_digits(dim_x, dim_y)
         data_native = seq_items_xform(data, lambda v: float(v))
         local_data = {"array": data}
 
@@ -486,12 +499,24 @@ class TestPropArrayMultiDimensional(unittest.TestCase):
         def set_fn(id_arg, value):
             local_data["array"] = value
 
-        id_type.temp = FloatVectorProperty(size=(4, 4), subtype='MATRIX', get=get_fn, set=set_fn)
+        id_type.temp = FloatVectorProperty(size=(dim_x, dim_y), subtype='MATRIX', get=get_fn, set=set_fn)
         id_inst.temp = data_native
         data_as_tuple = seq_items_as_tuple(id_inst.temp)
         self.assertEqual(data_as_tuple, data_native)
         del id_type.temp
 
+    def test_matrix_3x3(self):
+        self._test_matrix(3, 3)
+
+    def test_matrix_4x4(self):
+        self._test_matrix(4, 4)
+
+    def _test_matrix_with_callbacks_3x3(self):
+        self._test_matrix_with_callbacks(self, 3, 3)
+
+    def _test_matrix_with_callbacks_4x4(self):
+        self._test_matrix_with_callbacks(self, 4, 4)
+
 
 class TestPropArrayDynamicAssign(unittest.TestCase):
     """