[3/4] (Try2) msi: Fix ACTION_AppSearchDr on empty path.

[Nicolas Le Cam]

This one fixes msi DrLocator on empty paths, and consequently on
relative paths. This allows latest patch to be free of todo_wine for the
empty path corner case.

The problem was that deformat_string, which is called by
ACTION_ExpandAnyPath, is calling build_default_format on empty string,
producing something like L"1:  " as a result that was expanded with a
trailing backslash producing unexpected values.

Skipping ACTION_ExpandAnyPath on empty path resolves the problem but I
was needing my previous msi patch fixing MSI_RecordGetStringW (commit
e00d864a35ff9739fc55d73d869f69c0067d0bce) to be accepted to be able to
use the buffer size returned by MsiRecordGetStringW.

--
Nicolas Le Cam