[Phi]fix split error when sections has 0 size and add test case (#41708)

* fix split error when sections has 0 size and add test case

* fix test case

paddle/fluid/operators/strided_memcpy.h

@@ -134,7 +134,7 @@ inline void StridedMemcpyWithAxis0(
   for (size_t i = 0; i < outputs->size(); ++i) {
     auto out_stride = stride_numel(shape_refer[i]->dims());
     auto out = outputs->at(i);
-    if (out != nullptr) {
+    if (out != nullptr && out->initialized()) {
       StridedNumelCopyWithAxis<T>(dev_ctx, axis, out->data<T>(), out_stride,
                                   input.data<T>() + input_offset, in_stride,
                                   out_stride[axis]);

python/paddle/fluid/tests/unittests/test_split_op.py

@@ -459,5 +459,24 @@ class API_TestDygraphSplit(unittest.TestCase):
         self.assertTrue(np.allclose(ex_x2, x2_out))
 
 
+class API_TestEmptySplit(unittest.TestCase):
+    def test_axis_input_empty_section(self):
+        with fluid.dygraph.guard():
+            input_1 = np.random.random([8, 6, 6]).astype("float32")
+            # input is a variable which shape is [8, 6, 6]
+            input = paddle.to_tensor(input_1)
+            x0, x1, x2 = paddle.split(input, num_or_sections=[5, 0, 3])
+            x0_out = x0.numpy()
+            x1_out = x1.numpy()
+            x2_out = x2.numpy()
+            ex_x0, ex_x1, ex_x2 = np.split(input_1, [
+                5,
+                5,
+            ])
+        self.assertTrue(np.allclose(ex_x0, x0_out))
+        self.assertTrue(np.allclose(ex_x1, x1_out))
+        self.assertTrue(np.allclose(ex_x2, x2_out))
+
+
 if __name__ == '__main__':
     unittest.main()