Blender Git Loki

Fix T67078: Crash with vertex slide and multi-objects

If one of the objects had invalid selected edges, it would lead to a
crash since none of the for loops were checking for whether the edge
slide data is valid.

We could refactor the macros to create a new
FOREACH_TRANS_DATA_CONTAINER_WITH_DATA

However we are too close to 2.80 final release so we manually skip them
for now.

Note: TRANS_DATA_CONTAINER_FIRST_OK cannot be used either for the same
reason.

Reviewers: campbellbarton

Differential Revision: https://developer.blender.org/D5274