when camera preview is open, the preview toggle button will close the preview

closes #3574

src/org/thoughtcrime/securesms/ConversationActivity.java

@@ -1370,8 +1370,12 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
   private class QuickAttachmentToggleListener implements OnClickListener {
     @Override
     public void onClick(View v) {
+      if (!quickAttachmentDrawer.isShowing()) {
         composeText.clearFocus();
         container.show(composeText, quickAttachmentDrawer);
+      } else {
+        container.hideAttachedInput(false);
+      }
     }
   }