Add default: break; to switches on SDL_Event::type

This is just a nice-to-have, as `SDL_Event::type` in an `Uint32`, so there are no
compiler errors about not handling all `SDL_EventType` enum values.

test/testhittesting.c

@@ -153,6 +153,8 @@ int main(int argc, char **argv)
             case SDL_EVENT_QUIT:
                 done = 1;
                 break;
+            default:
+                break;
             }
         }