AIDEGen: Fix the bug of unable to run aidegen_unittests

Bug: 140537750
Test: atest -v aidegen_unittests --host should pass
Change-Id: Id6e43d751e9b0fabfeacee904dfd5c90a98e874e
diff --git a/aidegen/lib/config_unittest.py b/aidegen/lib/config_unittest.py
index a31ad78..5491dae 100644
--- a/aidegen/lib/config_unittest.py
+++ b/aidegen/lib/config_unittest.py
@@ -103,14 +103,20 @@
         self.assertTrue(mock_read.called)
         self.assertTrue(mock_gen.called)
 
+    @mock.patch('os.stat')
     @mock.patch.object(common_util, 'file_generate')
     @mock.patch('os.path.exists')
-    def test_gen_empty_androidmanifest(self, mock_exists, mock_gen):
+    def test_gen_empty_androidmanifest(self, mock_exists, mock_gen, mock_stat):
         """Test _gen_empty_androidmanifest."""
         cfg = config.AidegenConfig()
         mock_exists.return_value = True
+        mock_stat.return_value.st_size = 1
         cfg._gen_empty_androidmanifest()
         self.assertFalse(mock_gen.called)
+        mock_exists.return_value = True
+        mock_stat.return_value.st_size = 0
+        cfg._gen_empty_androidmanifest()
+        self.assertTrue(mock_gen.called)
         mock_exists.return_value = False
         cfg._gen_empty_androidmanifest()
         self.assertTrue(mock_gen.called)