Improving handling of uploadFailedSarifResult -> [Object object]

src/init-action-post-helper.ts

@@ -171,9 +171,10 @@ export async function run(
     process.env["CODEQL_ACTION_EXPECT_UPLOAD_FAILED_SARIF"] === "true" &&
     !uploadFailedSarifResult.raw_upload_size_bytes
   ) {
+    const error = JSON.stringify(uploadFailedSarifResult);
     throw new Error(
       "Expected to upload a failed SARIF file for this CodeQL code scanning run, " +
-        `but the result was instead ${uploadFailedSarifResult}.`
+        `but the result was instead ${error}.`
     );
   }