Remove unncessary assert.

It was possible that when deleting elements the selection becomes invalid. That
resulted in the assert being caused on occasion. There's no need for the assert,
it could very easily just become a filtering mechanism to ensure the new
selection is still valid. This patch fixes that.

Change-Id: I3c48f94c3c7c312cbd534df03a20292ef6211b20
Merge topic 'fix_unnecessary_assert' into master

953a5979 Remove unncessary assert.