SVGFilter::implGenerateMetaData check page before use

Avoid crash in online impress:
1. session A edits the textbox
2. session B removed slide which is edited by A
3. session A tries to edit another textbox on other slide

Change-Id: Ic875321107baa48fd2a5b52aa2580a8fcde40823
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/113077
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/114203
Tested-by: Jenkins
Reviewed-by: Szymon Kłos <szymon.klos@collabora.com>

0 files changed, 0 insertions, 0 deletions