Don't show placeholder for sent media

Session/Conversations/ConversationVC+Interaction.swift

@@ -382,7 +382,8 @@ extension ConversationVC : InputViewDelegate, MessageCellDelegate, ContextMenuAc
             case .mediaMessage:
                 guard let index = viewItems.firstIndex(where: { $0 === viewItem }),
                     let cell = messagesTableView.cellForRow(at: IndexPath(row: index, section: 0)) as? VisibleMessageCell else { return }
-                if let thread = self.thread as? TSContactThread,
+                if viewItem.interaction is TSIncomingMessage,
+                    let thread = self.thread as? TSContactThread,
                     Storage.shared.getContact(with: thread.contactIdentifier())?.isTrusted != true {
                     // Ask the user whether they want to download this attachment
                     let modal = DownloadAttachmentModal(viewItem: viewItem)

Session/Conversations/Message Cells/VisibleMessageCell.swift

@@ -337,7 +337,8 @@ final class VisibleMessageCell : MessageCell, LinkPreviewViewDelegate {
                 stackView.pin(to: snContentView, withInset: inset)
             }
         case .mediaMessage:
-            if let thread = viewItem.interaction.thread as? TSContactThread,
+            if viewItem.interaction is TSIncomingMessage,
+                let thread = viewItem.interaction.thread as? TSContactThread,
                 Storage.shared.getContact(with: thread.contactIdentifier())?.isTrusted != true {
                 let mediaPlaceholderView = MediaPlaceholderView(viewItem: viewItem, textColor: bodyLabelTextColor)
                 snContentView.addSubview(mediaPlaceholderView)