Fix conversation list safety number change snippet for groups

Fixes #5985
Closes #6655
// FREEBIE

res/values/strings.xml

@@ -592,6 +592,7 @@
     <string name="ThreadRecord_media_message">Media message</string>
     <string name="ThreadRecord_s_joined_signal">%s joined Signal!</string>
     <string name="ThreadRecord_disappearing_message_time_updated_to_s">Disappearing message time set to %s</string>
+    <string name="ThreadRecord_safety_number_changed">Safety number changed</string>
     <string name="ThreadRecord_your_safety_number_with_s_has_changed">Your safety number with %s has changed.</string>
 
     <!-- UpdateApkReadyListener -->

src/org/thoughtcrime/securesms/database/model/ThreadRecord.java

@@ -103,7 +103,8 @@ public class ThreadRecord extends DisplayRecord {
       String time = ExpirationUtil.getExpirationDisplayValue(context, (int) (getExpiresIn() / 1000));
       return emphasisAdded(context.getString(R.string.ThreadRecord_disappearing_message_time_updated_to_s, time));
     } else if (SmsDatabase.Types.isIdentityUpdate(type)) {
-      return emphasisAdded(context.getString(R.string.ThreadRecord_your_safety_number_with_s_has_changed, getRecipients().getPrimaryRecipient().toShortString()));
+      if (getRecipients().isGroupRecipient()) return emphasisAdded(context.getString(R.string.ThreadRecord_safety_number_changed));
+      else                                    return emphasisAdded(context.getString(R.string.ThreadRecord_your_safety_number_with_s_has_changed, getRecipients().getPrimaryRecipient().toShortString()));
     } else {
       if (TextUtils.isEmpty(getBody().getBody())) {
         return new SpannableString(emphasisAdded(context.getString(R.string.ThreadRecord_media_message)));