Allow cat of regression diff to fail

This matches a corresponding change in the CI
workflow file for RMG-Py, which was introduced
to account for very large differences between
the dynamic and baseline test results.

See: ReactionMechanismGenerator/RMG-Py#2316 (comment)

.github/workflows/CI.yml

@@ -208,7 +208,7 @@ jobs:
               export FAILED=Yes
             fi
             echo "" # blank line so next block is interpreted as markdown
-            cat "$regr_test-core.log"
+            cat "$regr_test-core.log" || (echo "Dumping the whole log failed, please download it from GitHub actions. Here are the first 100 lines:" && head -n100 "$regr_test-core.log")
             echo "</details>"
             echo "<details>"
             if python-jl scripts/checkModels.py \