find .apk properly

Author: MrCyjaneK

.github/workflows/pr_test_build_android.yml

@@ -281,7 +281,8 @@ jobs:
       - name: Find APK file
         id: find_apk
         run: |
-          apk_file=$(ls ${{ github.workspace }}/build/app/outputs/flutter-apk/test-apk/*_slack.apk || echo "")
+          set -x
+          apk_file=$(ls build/app/outputs/flutter-apk/test-apk/*_slack.apk || exit 1)
           echo "APK_FILE=$apk_file" >> $GITHUB_ENV
         
       - name: Send Test APK