ASSIGN_T uses 0 as right hand side value if eval_expr() returns

with error. That means, the expression evaluation result is false in case
of any error.

action.c

@@ -813,6 +813,7 @@ int do_action(struct run_act_ctx* h, struct action* a, struct sip_msg* msg)
 						break;
 					} else {
 						LOG(L_WARN,"WARNING: do_action: error in expression\n");
+						v = 0; /* error is treated as false (Miklos) */
 					}
 				}