patch 8.0.1423: error in return not caught by try/catch

Problem:    Error in return not caught by try/catch.
Solution:   Call update_force_abort(). (Yasuhiro Matsomoto, closes #2483)

src/userfunc.c

@@ -2972,6 +2972,9 @@ ex_return(exarg_T *eap)
     /* It's safer to return also on error. */
     else if (!eap->skip)
     {
+	/* In return statement, cause_abort should be force_abort. */
+	update_force_abort();
+
 	/*
 	 * Return unless the expression evaluation has been cancelled due to an
 	 * aborting error, an interrupt, or an exception.