Check if room is a DM before showing the join chat button

app/src/main/java/chat/rocket/android/chatroom/ui/ChatRoomFragment.kt

@@ -31,6 +31,8 @@ import chat.rocket.android.helper.KeyboardHelper
 import chat.rocket.android.helper.MessageParser
 import chat.rocket.android.util.extensions.*
 import chat.rocket.android.widget.emoji.*
+import chat.rocket.common.model.RoomType
+import chat.rocket.common.model.roomTypeOf
 import chat.rocket.core.internal.realtime.socket.model.State
 import chat.rocket.core.model.ChatRoom
 import dagger.android.support.AndroidSupportInjection
@@ -646,7 +648,7 @@ class ChatRoomFragment : Fragment(), ChatRoomView, EmojiKeyboardListener, EmojiR
         if (isChatRoomReadOnly && !canPost) {
             text_room_is_read_only.setVisible(true)
             input_container.setVisible(false)
-        } else if (!isSubscribed) {
+        } else if (!isSubscribed && roomTypeOf(chatRoomType) != RoomType.DIRECT_MESSAGE) {
             input_container.setVisible(false)
             button_join_chat.setVisible(true)
             button_join_chat.setOnClickListener { presenter.joinChat(chatRoomId) }