[backport/2.6][!366] [LocalMatrix] fix iteration when cols == 0
Merge branch 'feature/check-lfs-size-before-scatter' into 'master'
When the local matrix has 0 columns, the iterators where not set up correctly. This merge request fixes this issue by returning the begin iterator as end iterator in such a case.
See merge request pdelab/dune-pdelab!366
(cherry picked from commit 6fb2aa30)
212ad793 [TestLocalMatrix] add a test for local matrix 9eda6d11 [LocalMatrix] fix corner case of zero columns afec9380 [TestLocalMatrix] remove try catch block
Edited by Steffen Müthing