Relax code style check for NULL

This is fine tuned to allow the string in the last commit to pass this
check, but still generally makes sense too.

.github/workflows/code_checks.yml

@@ -93,7 +93,7 @@ jobs:
             git fetch --depth=1 origin master
             if git diff origin/master \
                ':**.h' ':**.cpp' \
-               | grep -E '^\+.*(wxOVERRIDE|wxNOEXCEPT|[^"_@A-Za-z0-9]NULL[^"_A-Za-z0-9])'; then
+               | grep -E '^\+.*(wxOVERRIDE|wxNOEXCEPT|[^"_@A-Za-z0-9]NULL([- ,;()+*/%&=!?]|$))'; then
               echo "::error ::Please use C++11 equivalents of the deprecated macros in the new code."
               exit 1
             fi