Fix delete in search resource

[tintinthong]

Essentially, the instances array returned from the search resource [undefined, ...] bcos of the delete action

[github-actions]

Host Test Results

    1 files  ±0      1 suites  ±0   20m 35s ⏱️ +6s
721 tests ±0  719 ✔️ ±0  2 💤 ±0  0 ❌ ±0 
726 runs  ±0  724 ✔️ ±0  2 💤 ±0  0 ❌ ±0 

Results for commit fa5665d. ± Comparison against base commit cfd2579.

[tintinthong]

Its likely this is a workaround that doesn't address the original issue

[tintinthong]

After pairing session with @habdelra, the main reason is that card resources clear the card instance upon receiving a 404 (assuming the card has deleted).

boxel/packages/host/app/resources/card-resource.ts

Line 389 in fa5665d

this.clearCardInstance();

The current fix is correct to only return searches that has card instances