Allow dismissing discard draft dialog

app/src/main/java/eu/faircode/email/FragmentCompose.java

@@ -589,6 +589,12 @@ public class FragmentCompose extends FragmentEx {
                     .setNegativeButton(R.string.title_no, new DialogInterface.OnClickListener() {
                         @Override
                         public void onClick(DialogInterface dialog, int which) {
+                            dialog.dismiss();
+                        }
+                    })
+                    .setOnDismissListener(new DialogInterface.OnDismissListener() {
+                        @Override
+                        public void onDismiss(DialogInterface dialog) {
                             finish();
                         }
                     })