Daap::Reader: Don't use QList::[ on unreliable input, use ::value()

This should fix bug 280774, but I don't use DAAP collection, do I'm
shooting blindly.

BUGFIXES:
 * Fix crash related to DAAP collection.

Reporters, if this doesn't solve your bug, please reopen.

BUG: 280774
FIXED-IN: 2.6
DIGEST: bugfix