no need to send sync messages when only 1 device

// FREEBIE

src/Messages/OWSMessageSender.m

@@ -1089,10 +1089,16 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
 - (void)handleMessageSentLocally:(TSOutgoingMessage *)message
 {
     if (message.shouldSyncTranscript) {
-        // TODO: I suspect we shouldn't optimistically set hasSyncedTranscript.
+        __block BOOL hasSecondaryDevices = NO;
-        //       We could set this in a success handler for [sendSyncTranscriptForMessage:].
+        [self.dbConnection readWithBlock:^(YapDatabaseReadTransaction *_Nonnull transaction) {
-        [message updateWithHasSyncedTranscript:YES];
+            hasSecondaryDevices = [OWSDevice hasSecondaryDevicesWithTransaction:transaction];
-        [self sendSyncTranscriptForMessage:message];
+        }];
+        if (hasSecondaryDevices) {
+            // TODO: I suspect we shouldn't optimistically set hasSyncedTranscript.
+            //       We could set this in a success handler for [sendSyncTranscriptForMessage:].
+            [message updateWithHasSyncedTranscript:YES];
+            [self sendSyncTranscriptForMessage:message];
+        }
     }
 
     [OWSDisappearingMessagesJob setExpirationForMessage:message];