Fixed busy loop in case of partially malformed rtcp packet

BUG=webrtc:5574

Review URL: https://codereview.webrtc.org/1726573003

Cr-Commit-Position: refs/heads/master@{#11946}

webrtc/modules/rtp_rtcp/source/rtcp_utility.cc

@@ -230,6 +230,7 @@ RTCPUtility::RTCPParserV2::IterateTopLevel()
         {
           if (!ParseFBCommon(header)) {
             // Nothing supported found, continue to next block!
+            EndCurrentBlock();
             break;
           }
           return;