BUG: Fix bad write in masked iterator output copy paths

There was an unfortunate typo which leads to writing too many values
back when wheremask is used in a non-continguous N-D context.

Closes numpygh-19589

Author: seberg

numpy/core/src/multiarray/lowlevel_strided_loops.c.src

@@ -1316,7 +1316,7 @@ PyArray_TransferMaskedStridedToNDim(npy_intp ndim,
                 args, &count, strides, mask, mask_stride, cast_info->auxdata);
     }
     int res = stransfer(&cast_info->context,
-            args, &count, strides, mask, mask_stride, cast_info->auxdata);
+            args, &N, strides, mask, mask_stride, cast_info->auxdata);
     if (res < 0) {
         return -1;
     }

numpy/core/tests/test_nditer.py

@@ -2738,7 +2738,12 @@ def _is_buffered(iterator):
 @pytest.mark.parametrize("a",
         [np.zeros((3,), dtype='f8'),
          np.zeros((9876, 3*5), dtype='f8')[::2, :],
-         np.zeros((4, 312, 124, 3), dtype='f8')[::2, :, ::2, :]])
+         np.zeros((4, 312, 124, 3), dtype='f8')[::2, :, ::2, :],
+         # Also test with the last dimension strided (so it does not fit if
+         # there is repeated access)
+         np.zeros((9,), dtype='f8')[::3],
+         np.zeros((9876, 3*10), dtype='f8')[::2, ::5],
+         np.zeros((4, 312, 124, 3), dtype='f8')[::2, :, ::2, ::-1]])
 def test_iter_writemasked(a):
     # Note, the slicing above is to ensure that nditer cannot combine multiple
     # axes into one.  The repetition is just to make things a bit more