Avoid crash on changing snap mode when no animation exists, closes #28031

(cherry picked from commit 0d41f8fb00e72e5c6b3e1186530e5c92761074e6)

editor/animation_track_editor.cpp

@@ -2466,6 +2466,7 @@ void AnimationTrackEditor::set_animation(const Ref<Animation> &p_anim) {
 		step->set_block_signals(false);
 		step->set_read_only(false);
 		snap->set_disabled(false);
+		snap_mode->set_disabled(true);
 	} else {
 		hscroll->hide();
 		edit->set_disabled(true);
@@ -2474,6 +2475,7 @@ void AnimationTrackEditor::set_animation(const Ref<Animation> &p_anim) {
 		step->set_block_signals(false);
 		step->set_read_only(true);
 		snap->set_disabled(true);
+		snap_mode->set_disabled(false);
 	}
 }