Fixed bug 3701 - WM_TOUCH message may cause calls to null if touch functions are not properly loaded

Simon Hug

When WIN_WindowProc processes the WM_TOUCH message, it doesn't check if the touch functions have been properly loaded and may call a NULL pointer. It's probably an extremely rare case, but here's a patch that adds some checks anyway.

src/video/windows/SDL_windowsevents.c

@@ -884,7 +884,7 @@ WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
         break;
 
     case WM_TOUCH:
-        {
+        if (data->videodata->GetTouchInputInfo && data->videodata->CloseTouchInputHandle) {
             UINT i, num_inputs = LOWORD(wParam);
             PTOUCHINPUT inputs = SDL_stack_alloc(TOUCHINPUT, num_inputs);
             if (data->videodata->GetTouchInputInfo((HTOUCHINPUT)lParam, num_inputs, inputs, sizeof(TOUCHINPUT))) {