Hide webxdc attach button for channels (#4402)

src/main/java/org/thoughtcrime/securesms/ConversationActivity.java

@@ -1116,6 +1116,7 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
     if (chatId == DcChat.DC_CHAT_NO_CHAT)
       throw new IllegalStateException("can't display a conversation for no chat.");
     dcChat = DcHelper.getContext(context).getChat(chatId);
+    attachmentTypeSelector = null;
     recipient = new Recipient(this, dcChat);
     glideRequests = GlideApp.with(this);
 

src/main/java/org/thoughtcrime/securesms/components/AttachmentTypeSelector.java

@@ -92,6 +92,10 @@ public class AttachmentTypeSelector extends PopupWindow {
       ViewUtil.findById(layout, R.id.location_linear_layout).setVisibility(View.GONE);
     }
 
+    if (DcHelper.getContext(context).getChat(chatId).isOutBroadcast()) {
+      ViewUtil.findById(layout, R.id.webxdc_linear_layout).setVisibility(View.GONE);
+    }
+
     setLocationButtonImage(context);
 
     setContentView(layout);