Avoid div0 in rare situation.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4382 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/server/net/ConnectionManager.java

@@ -213,6 +213,10 @@ public class ConnectionManager extends LoopingThread
             _lastStats = stats;
         }
 
+        // make sure we don't div0 if this method somehow gets called twice in
+        // the same millisecond
+        sinceLast = Math.max(sinceLast, 1L);
+
         report.append("* presents.net.ConnectionManager:\n");
         report.append("- Network connections: ");
         report.append(connects).append(" connects, ");