[REVIEW-3-6] don't use uninitialized global variable in lotus filter

[Markus Mohrhard]

Hey,

[1] fixes a crash opening lotus files. This regression has been
introduced by c75e2ed27d5da71891ed7a148ff9603c58eaa58e. The global
variable pLotusRoot is not yet assigned. I removed the use of the
global variable in the problematic class and replaced it with a local
variable.

Regards,
Markus

[1] http://cgit.freedesktop.org/libreoffice/core/commit/?id=2ac26e6b5248f2f3fde8dc4341b01ef15b6c3a29