src: Don't process rel=preload again once we found it

src/http2.cc

@@ -924,6 +924,7 @@ parse_next_link_header_once(const char *first, const char *last) {
     // we expect link-param
 
     if (!ign) {
+      if (!ok) {
         // rel can take several relations using quoted form.
         static constexpr char PLP[] = "rel=\"";
         static constexpr size_t PLPLEN = str_size(PLP);
@@ -958,7 +959,7 @@ parse_next_link_header_once(const char *first, const char *last) {
             start = first;
           }
           if (first == last) {
-          return {{StringRef{}}, first};
+            return {{StringRef{}}, last};
           }
           assert(*first == '"');
           ++first;
@@ -972,6 +973,7 @@ parse_next_link_header_once(const char *first, const char *last) {
           }
           return {{StringRef{}}, last};
         }
+      }
       // we are only interested in rel=preload parameter.  Others are
       // simply skipped.
       static constexpr char PL[] = "rel=preload";