Make sure we have XShape symbols before we allow a shaped window.

src/video/x11/SDL_x11shape.c

@@ -27,7 +27,9 @@
 #include "SDL_x11video.h"
 
 SDL_WindowShaper* X11_CreateShaper(SDL_Window* window) {
-	SDL_WindowShaper* result = malloc(sizeof(SDL_WindowShaper));
+	SDL_WindowShaper* result = NULL;
+	if (SDL_X11_HAVE_XSHAPE) {  /* Make sure X server supports it. */
+		result = malloc(sizeof(SDL_WindowShaper));
 		result->window = window;
 		result->alphacutoff = 0;
 		result->usershownflag = 0;
@@ -35,6 +37,8 @@ SDL_WindowShaper* X11_CreateShaper(SDL_Window* window) {
 		window->shaper = result;
 		int resized_properly = X11_ResizeWindowShape(window);
 		assert(resized_properly == 0);
+	}
+
 	return result;
 }