finish ConversationActivity on delete of empty thread

Fixes #3086
Closes #3124

// FREEBIE

src/org/thoughtcrime/securesms/ConversationActivity.java

@@ -504,10 +504,10 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
       public void onClick(DialogInterface dialog, int which) {
         if (threadId > 0) {
           DatabaseFactory.getThreadDatabase(ConversationActivity.this).deleteConversation(threadId);
-          composeText.getText().clear();
-          threadId = -1;
-          finish();
         }
+        composeText.getText().clear();
+        threadId = -1;
+        finish();
       }
     });