[SVG] Fix problem when style's parent contains a mask element

Commits:

1. https://cgit.freedesktop.org/libreoffice/core/commit/?id=ecc7f698b5f080530f006218fa3dd82da43d9abb
2. https://cgit.freedesktop.org/libreoffice/core/commit/?id=3daee9953da215fb7c0740259dcb37713dd17cd1

Sample File: https://bug-attachments.documentfoundation.org/attachment.cgi?id=122721

Results:

Libreoffice 5.1

Libreoffice 5.2