Check for nullptr expression in parse_precedence function

modules/gdscript/gdscript_parser.cpp

@@ -2107,7 +2107,7 @@ GDScriptParser::ExpressionNode *GDScriptParser::parse_precedence(Precedence p_pr
 	ExpressionNode *previous_operand = (this->*prefix_rule)(nullptr, p_can_assign);
 
 	while (p_precedence <= get_rule(current.type)->precedence) {
-		if (p_stop_on_assign && current.type == GDScriptTokenizer::Token::EQUAL) {
+		if (previous_operand == nullptr || (p_stop_on_assign && current.type == GDScriptTokenizer::Token::EQUAL)) {
 			return previous_operand;
 		}
 		// Also switch multiline mode on here for infix operators.