fix the div 0 error of sparse_embedding (PaddlePaddle#49948)

* fix the div 0 error of sparse_embedding

* add unittest

python/paddle/fluid/contrib/layers/nn.py

@@ -793,6 +793,9 @@ def sparse_embedding(
         'paddle.static.nn.sparse_embedding',
     )
 
+    if input.size == 0:
+        raise ValueError("input size should not be 0")
+
     w = helper.create_parameter(
         attr=helper.param_attr,
         shape=size,

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

@@ -0,0 +1,37 @@
+#  Copyright (c) 2023 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+import paddle
+
+
+class TestSparseEmbeddingAPIError(unittest.TestCase):
+    def test_errors(self):
+        with paddle.fluid.dygraph.guard():
+            # The size of input in sparse_embedding should not be 0.
+            def test_0_size():
+                input = paddle.to_tensor([], dtype='int64')
+                paddle.static.nn.sparse_embedding(
+                    input,
+                    [2097152, 2097152, 2097152, 2097152],
+                    padding_idx=2097152,
+                )
+
+            self.assertRaises(ValueError, test_0_size)
+
+
+if __name__ == '__main__':
+    paddle.enable_static()
+    unittest.main()