emscripten: Fixed not removing pointer lock event callback.

src/video/emscripten/SDL_emscriptenevents.c

@@ -676,6 +676,8 @@ Emscripten_UnregisterEventHandlers(SDL_WindowData *data)
     emscripten_set_touchmove_callback("#canvas", NULL, 0, NULL);
     emscripten_set_touchcancel_callback("#canvas", NULL, 0, NULL);
 
+    emscripten_set_pointerlockchange_callback(NULL, NULL, 0, NULL);
+
     const char *target = SDL_GetHint(SDL_HINT_EMSCRIPTEN_KEYBOARD_ELEMENT);
     if (!target) {
         target = "#window";
@@ -683,7 +685,6 @@ Emscripten_UnregisterEventHandlers(SDL_WindowData *data)
 
     emscripten_set_keydown_callback(target, NULL, 0, NULL);
     emscripten_set_keyup_callback(target, NULL, 0, NULL);
-
     emscripten_set_keypress_callback(target, NULL, 0, NULL);
 
     emscripten_set_fullscreenchange_callback("#document", NULL, 0, NULL);