test capi: fix memory leak.

Delete the paint which is not committed properly.

test/capi/capiSavers.cpp

@@ -69,6 +69,8 @@ TEST_CASE("Save a paint into a file", "[capiSaver]")
     REQUIRE(tvg_saver_save(saver, paint3, TEST_DIR"/test.tvg", false) == TVG_RESULT_INSUFFICIENT_CONDITION);
 
     REQUIRE(tvg_saver_del(saver) == TVG_RESULT_SUCCESS);
+
+    tvg_paint_del(paint_empty);
 }
 
 TEST_CASE("Synchronize a Saver", "[capiSaver]")