Fix error when trying to call existing sigint handler which might be signal.SIG_IGN (#851)

* Fix error when trying to call existing sigint handler which might be signal.SIG_IGN

* update changelog

Author: daniel-wer

cluster_tools/Changelog.md

@@ -16,6 +16,7 @@ For upgrade instructions, please check the respective *Breaking Changes* section
 ### Changed
 
 ### Fixed
+- Fixed `TypeError` when aborting a run that occurred under certain circumstances. [#851](https://github.com/scalableminds/webknossos-libs/pull/851)
 
 
 ## [0.11.1](https://github.com/scalableminds/webknossos-libs/releases/tag/v0.11.1) - 2023-01-05

cluster_tools/cluster_tools/schedulers/cluster_executor.py

@@ -128,6 +128,7 @@ def handle_kill(self, existing_sigint_handler, signum, frame):
         if (
             existing_sigint_handler  # pylint: disable=comparison-with-callable
             != signal.default_int_handler
+            and callable(existing_sigint_handler)  # Could also be signal.SIG_IGN
         ):
             existing_sigint_handler(signum, frame)