Fix #34507, adding reroute node into invalid links would crash the compositor.

Compositor relies on correctly tagged invalid links, but the nodeInternalRelink function used to replace reroute nodes in localization did not correctly take this flag into account. If a node replaces a link with an invalid upstream link the resulting link must also be flagged invalid.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55047 954f8c5b-7b00-dc11-b283-0030488c597c
Sanity check in the cut-links operator, make sure preview jobs are not running before modifying the node tree.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55048 954f8c5b-7b00-dc11-b283-0030488c597c