Fix unread indirect mention bg color

The background color for the indirect unread mention counter was alwasys
white. Also in dark mode.

Now the background color is defined via the 'bg_default' color.

Signed-off-by: Tim Krüger <t@timkrueger.me>

app/src/main/java/com/nextcloud/talk/adapters/items/ConversationItem.java

@@ -155,8 +155,7 @@ public class ConversationItem extends AbstractFlexibleItem<ConversationItem.Conv
                         holder.dialogUnreadBubble.setChipBackgroundColorResource(R.color.colorPrimary);
                         holder.dialogUnreadBubble.setTextColor(Color.WHITE);
                     } else {
-                        holder.dialogUnreadBubble.setChipBackgroundColor(ColorStateList.valueOf(
-                            ContextCompat.getColor(context, R.color.white)));
+                        holder.dialogUnreadBubble.setChipBackgroundColorResource(R.color.bg_default);
                         holder.dialogUnreadBubble.setTextColor(ContextCompat.getColor(
                             context,
                             R.color.colorPrimary));