Missing notehead case related to nested square brackets

[craigsapp]

In this example:

**kern
!!LO:TX:tempo:a:t=[Langsame]\n[[half-dot] = [half] = 56]
1c
=
1d
=
1e
=
1f
==
*-

The [half-dot] is showing instead as only a [dot]:

When the outer square brackets are removed, the half note is displayed:

**kern
!!LO:TX:tempo:a:t=[Langsame]\n[half-dot] = [half] = 56
1c
=
1d
=
1e
=
1f
==
*-

[craigsapp]

Now working with recent commits: