fix debug crash

SignalServiceKit/src/Messages/OWSMessageHandler.m

@@ -71,6 +71,8 @@ NSString *envelopeAddress(SSKProtoEnvelope *envelope)
         return [NSString stringWithFormat:@"<NullMessage: %@ />", content.nullMessage];
     } else if (content.receiptMessage) {
         return [NSString stringWithFormat:@"<ReceiptMessage: %@ />", content.receiptMessage];
+    } else if (content.typingMessage) {
+        return [NSString stringWithFormat:@"<TypingMessage: %@ />", content.typingMessage];
     } else {
         // Don't fire an analytics event; if we ever add a new content type, we'd generate a ton of
         // analytics traffic.