1261 Some multi-char separators crash the app [#6102]

[chrisjj]

1 In Options, Library, Appearence, set Split multiple-value fields with: to "\\" without quotes (Mp3tag's display separator)
2 Restart MM

Expected: no hang.
Observed: hang.

Value "~~" likewise hangs. Value ", " does not, and displays as expected.

Tracked at http://www.ventismedia.com/mantis/view.php?id=6102