Fix issues in media gallery cells.

Signal/src/ViewControllers/ConversationView/Cells/OWSMessageBubbleView.m

@@ -809,7 +809,7 @@ const UIDataDetectorTypes kOWSAllowedDataDetectorTypes
 - (UIView *)loadViewForMedia
 {
     OWSAssertDebug(self.attachmentStream);
-    OWSAssertDebug([self.attachmentStream isImage]);
+    OWSAssertDebug([self.attachmentStream isVisualMedia]);
 
     ConversationMediaView *mediaView =
         [[ConversationMediaView alloc] initWithMediaCache:self.cellMediaCache attachment:self.attachmentStream];

SignalServiceKit/src/Messages/Interactions/TSMessage.m

@@ -217,7 +217,7 @@ static const NSUInteger OWSMessageSchemaVersion = 4;
 - (BOOL)isMediaGalleryWithTransaction:(YapDatabaseReadTransaction *)transaction
 {
     NSArray<TSAttachment *> *attachments = [self attachmentsWithTransaction:transaction];
-    if (attachments.count < 1) {
+    if (attachments.count < 2) {
         return NO;
     }
     for (TSAttachment *attachment in attachments) {