Bugfix: Set empty ignore nodes for IterativeSolver/LinearSolver

This was missing after the code shift to the external class.
It caused a segmentation fault when TNNMG is used with an
IterativeSolver/LinearSolver object.
2 jobs for add-ignore-nodes in 23 seconds (queued for 1 second)
latest
Status Name Job ID Coverage
  Test
failed dune:git--clang #11067

00:00:23

failed dune:git--gcc #11068

00:00:23

 
Name Stage Failure
failed
dune:git--clang Test There is an unknown failure, please try again
Running on runner-2aaf19c7-project-2559-concurrent-0 via runner...
Fetching changes...
HEAD is now at 5d5d9aa Bugfix: Set empty ignore nodes for IterativeSolver
From https://git.imp.fu-berlin.de/patrick.jaap_at_tu-dresden.de/dune-tnnmg
+ 5d5d9aa...54faab0 add-ignore-nodes -> origin/add-ignore-nodes (forced update)
Checking out 54faab07 as add-ignore-nodes...
Skipping Git submodules setup
/usr/bin/bash: line 6: echo: write error: No space left on device
ERROR: Job failed: exit code 1
failed
dune:git--gcc Test There is an unknown failure, please try again
Running on runner-2aaf19c7-project-2559-concurrent-1 via runner...
Fetching changes...
HEAD is now at 5d5d9aa Bugfix: Set empty ignore nodes for IterativeSolver
From https://git.imp.fu-berlin.de/patrick.jaap_at_tu-dresden.de/dune-tnnmg
+ 5d5d9aa...54faab0 add-ignore-nodes -> origin/add-ignore-nodes (forced update)
Checking out 54faab07 as add-ignore-nodes...
Skipping Git submodules setup
/usr/bin/bash: line 6: echo: write error: No space left on device
ERROR: Job failed: exit code 1