fix: try fix empty outputs

[skip ci]

.github/actions/acc_test/action.yaml

@@ -221,6 +221,16 @@ runs:
         echo "result=no result before run" >> "$GITHUB_OUTPUT"
 
         echo "Running acceptance tests for the terraform provider"
+
+        if [[ -z "$testfile" ]]; then
+          test_file="./..."
+        fi
+
+        if [[ -z "$testfile" ]]; then
+          echo "ERROR: No test file provided"
+          exit 1
+        fi
+
         set +e
         cd stackit || exit 1
         TF_ACC=1 \