balloonText and DoublePercentEngraver

[Werner LEMBERG]

Please have a look at the following example.

```
\new Score \with {
  \consists "Balloon_engraver"
} \new Staff {
  \repeat "percent" 2 {
    e'4 e' e' e' |
    \balloonGrobText #'PercentRepeat #'(0 . 1) \markup "Repeat"
  }

  \repeat "percent" 2 {
    e'2 e' | e' e' |
    \balloonGrobText #'DoublePercentRepeat #'(0 . 1) \markup "DoubleRepeat"
  }
}
```

This shows a balloon help for `PercentRepeat` but not for
`DoublePercentRepeat`.  What am I doing wrong?


    Werner