Update action.yml (#73)

action.yml

@@ -147,7 +147,7 @@ runs:
           echo "Input files: ${ALL_INPUT_FILES[@]}"
           echo "Matching modified files: ${ALL_MODIFIED_FILES[@]}"
 
-          if [[ ${#ALL_MODIFIED_FILES[@]} -gt 0 ]]; then
+          if [[ -n "$ALL_MODIFIED_FILES" ]]; then
             echo "::set-output name=any_changed::true"
           else
             echo "::set-output name=any_changed::false"