issue：ui_test_app.cpp:44:1: warning: non-void function does not return a value

non-void函数提供返回值，在函数的最后一行，增加：return nullptr;
Signed-off-by: twping <htdhym@yeah.net>

test/framework/src/ui_test_app.cpp

@@ -41,11 +41,7 @@ void* AutoTestThread(void*)
     AutoTestApp::GetInstance()->Start();
     AutoTestCaseGroup::TearDownTestCase();
     CompareTools::UnsetLogPath();
-#ifdef _WIN32
-    return 0;
-#else
     return nullptr;
-#endif
 }
 
 UITestApp* UITestApp::GetInstance()