fix aggregation logic

server/handler/snapshots.go

@@ -118,10 +118,14 @@ func (h *Handler) renderSnapshotList(w http.ResponseWriter, r *http.Request, sna
 		case "monthly":
 			group = record.SnapshotTime.Format("2006")
 		}
+		count := record.SnapshotCount
+		if count < 0 {
+			count = 0
+		}
 		entries = append(entries, views.SnapshotEntry{
 			Label: label,
 			Link:  "/reports/" + url.PathEscape(record.TableName) + ".xlsx",
-			Count: record.SnapshotCount,
+			Count: count,
 			Group: group,
 		})
 	}