Avoid retrieving the object ID of a Nil variable

editor/debugger/editor_debugger_inspector.cpp

@@ -232,7 +232,7 @@ void EditorDebuggerInspector::add_stack_variable(const Array &p_array) {
 	PropertyHint h = PROPERTY_HINT_NONE;
 	String hs;
 
-	if (var.var_type == Variant::OBJECT) {
+	if (var.var_type == Variant::OBJECT && v) {
 		v = Object::cast_to<EncodedObjectAsID>(v)->get_object_id();
 		h = PROPERTY_HINT_OBJECT_ID;
 		hs = "Object";