imap: add a check for Curl_meta_get()

[bagder]

It should not return NULL, but if it does we need to bail out. Like we do elsewhere.a

Found by CodeSonar.

[bagder]

augment review

[bagder]

@aisle-analyzer review

[aisle-research-bot]

🔒 Aisle Security Analysis

✅ We scanned this PR and did not find any security vulnerabilities.
_{Aisle supplements but does not replace security review.}

---

Analyzed PR: #20510 at commit 81ac0c2

[augmentcode]

🤖 Augment PR Summary

Summary: Adds a defensive NULL-check after fetching the per-easy IMAP metadata in the LIST/SEARCH response handler.

Why: Ensures the state machine bails out safely if Curl_meta_get() unexpectedly returns NULL (as flagged by CodeSonar), avoiding a potential NULL dereference.

_{🤖 Was this summary useful? React with 👍 or 👎}

[augmentcode]

Review completed. No suggestions at this time.

Comment augment review to trigger a new review at any time.