Gui: relax some asserts in view (#2623)

* Remove assertion preventing replacement of view input callback
* Gui: relax some asserts in view

Co-authored-by: あく <alleteam@gmail.com>

applications/services/gui/view.c

@@ -19,19 +19,16 @@ void view_tie_icon_animation(View* view, IconAnimation* icon_animation) {
 
 void view_set_draw_callback(View* view, ViewDrawCallback callback) {
     furi_assert(view);
-    furi_assert(view->draw_callback == NULL);
     view->draw_callback = callback;
 }
 
 void view_set_input_callback(View* view, ViewInputCallback callback) {
     furi_assert(view);
-    furi_assert(view->input_callback == NULL);
     view->input_callback = callback;
 }
 
 void view_set_custom_callback(View* view, ViewCustomCallback callback) {
     furi_assert(view);
-    furi_assert(callback);
     view->custom_callback = callback;
 }
 
@@ -62,7 +59,6 @@ void view_set_update_callback_context(View* view, void* context) {
 
 void view_set_context(View* view, void* context) {
     furi_assert(view);
-    furi_assert(context);
     view->context = context;
 }