xmlhelp: fix reading symlinked .tree files
xmlhelp: fix reading symlinked .tree files

Apparently the .tree files nowadays are symlinked, which was not the
case on the libreoffice-4-0 branch... and on viewing the Contents tab
it's evident we can't actually read symlinked .tree files, and crash
with an STL assert because the children vector is empty.

Change-Id: I5a543ef85b827e194120530a486cf19a76837d87

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core