propagate error when adding domain condition

app/router/config.go

@@ -54,7 +54,9 @@ func (rr *RoutingRule) BuildCondition() (Condition, error) {
 	if len(rr.Domain) > 0 {
 		matcher := NewCachableDomainMatcher()
 		for _, domain := range rr.Domain {
-			matcher.Add(domain)
+			if err := matcher.Add(domain); err != nil {
+				return nil, newError("failed to build domain condition").Base(err)
+			}
 		}
 		conds.Add(matcher)
 	}