mpool/repub: only record in journal if actually repubbing.

chain/messagepool/messagepool.go

@@ -371,6 +371,7 @@ func (mp *MessagePool) runLoop() {
 				log.Errorf("errors while republishing: %+v", errout)
 			}
 
+			if len(outputMsgs) > 0 {
 				journal.MaybeRecordEvent(mp.jrnl, mp.evtTypes[evtTypeMpoolRepub], func() interface{} {
 					msgs := make([]MessagePoolEvt_Message, 0, len(outputMsgs))
 					for _, m := range outputMsgs {
@@ -382,6 +383,7 @@ func (mp *MessagePool) runLoop() {
 						Error:    errout,
 					}
 				})
+			}
 
 		case <-mp.pruneTrigger:
 			if err := mp.pruneExcessMessages(); err != nil {