Run Ktlint on a specific file

I have a Kotlin project configured with Ktlint. I am executing the command ./gradlew ktlintCheck to get reports from my code according to my .editorconfig file configured. Nonetheless, I would like to execute the ktlintCheck only over my changed files detected from git diff, but it is not working. Here is my script:

#!/bin/bash

BASE_BRANCH="main"

MODIFIED_FILES=$(git diff --name-only "$BASE_BRANCH" -- '*.kt')

if [ -n "$MODIFIED_FILES" ]; then
  echo "Running Ktlint..."
  echo "$MODIFIED_FILES" | xargs ./gradlew ktlintCheck
else
  echo "Any files detected"
fi

Theoretically, this script should get the changed files and run the ./gradlew ktlintCheck over them but is running over the project. Does somebody know how to fix it?

  - name: Get changed Kotlin files
    id: changed-files
    run: |
      echo "Retrieving changed files..."
      CHANGED_FILES=$(git diff --name-only --diff-filter=ACMR -- '*.kt' '*.kts' | tr '\n' ' ')
      echo "Changed files: $CHANGED_FILES"
      echo "::set-output name=changed_files::$CHANGED_FILES"

  - name: Run ktlint on changed files
    if: ${{ steps.changed-files.outputs.changed_files != '' }}
    run: |
      echo "Running ktlint on the following files:"
      echo "${{ steps.changed-files.outputs.changed_files }}"
      ./gradlew --quiet ktlintCheck -PinternalKtlintGitFilter="${{ steps.changed-files.outputs.changed_files }}"

  - name: No Kotlin files changed
    if: ${{ steps.changed-files.outputs.changed_files == '' }}
    run: echo "No Kotlin files were changed in this pull request."