rhbz#1072607: (hopefully) fix crash in SvxRuler::MouseMove()

Not sure why mpParaItem is 0 here, add a check like in every other
SvxRuler method.

(regression from 47a77d7dbc427e51421e2df8d59695834cb74980)

Change-Id: Ic11a4d0c9b6ca217cd59d1d3f6789592996d2c1d
fdo#74787, rhbz#1072553: fix Template Mananger import crash

File dialog causes call to ThumbnailView::LoseFocus() and clears
selected folders.

(regression from 0314034d8b23d5b69399cfcdf6b2f2add73f9f47)

Change-Id: Ic5f2602e9dd1d12aad8c68c48f6bbb119ee6492c