Flake8: oprava nekontrolování migrací v pre-commit

_git_hooks/pre-commit

@@ -10,6 +10,11 @@ status=0
 
 # select only changed python files which are not migrations
 changed=`git diff --cached --name-only | grep 'py$' | grep -v 'migrations/[0-9]'`
+if [ -z $changed ] ; then
+    # Nothing to check. Note the exit is necessary -- we would not pass any
+    # paths to git diff below and it would output the diff unfiltered.
+    exit 0
+fi
 
 git diff --unified=1 --cached HEAD -- $changed > $TMPDIFF