Empty commitments for blocks without any DA extrinsics

[ToufeeqP]

Pull Request type

Please add the labels corresponding to the type of changes your PR introduces:

• [x] Feature

Description

The commitments will be empty with grid dimension [0,0] for blocks without any DA transactions. This is also the case if for any reason commitment generation fails. In both scenarios, kate query_rows and query_proof RPCs return an error.

Checklist

• [x] I have performed a self-review of my own code.
• [x] The tests pass successfully with cargo test.
• [x] The code was formatted with cargo fmt.
• [x] The code compiles with no new warnings with cargo build --release and cargo build --release --features runtime-benchmarks.
• [x] The code has no new warnings when using cargo clippy.
• [x] If this change affects documented features or needs new documentation, I have created a PR with a documentation update.

[Leouarz]

you can merge, the failing benchmarking needs some update, i removed it from the main branch temporarily