Handle handle_modes being undefined by giving default values rather than flagging error

Author: TheSofox

scene/resources/animation.cpp

@@ -321,8 +321,12 @@ bool Animation::_set(const StringName &p_name, const Variant &p_value) {
 				Vector<real_t> times = d["times"];
 				Vector<real_t> values = d["points"];
 #ifdef TOOLS_ENABLED
-				ERR_FAIL_COND_V(!d.has("handle_modes"), false);
-				Vector<int> handle_modes = d["handle_modes"];
+				Vector<int> handle_modes;
+				if (d.has("handle_modes")) {
+					handle_modes = d["handle_modes"];
+				} else {
+					handle_modes.resize_zeroed(times.size());
+				}
 #endif // TOOLS_ENABLED
 
 				ERR_FAIL_COND_V(times.size() * 5 != values.size(), false);