"AttributeError: 'NoneType' object has no attribute 'decode'" when executing empty script

Nobody has claimed this yet.

Wouldn't it be natural that executing a script with only comments is a no-op returning OK?
Such that for example commenting out the contents of a migration script while developing runs the script as a no-op.

Instead what happens when running this:
```
import os
import asyncpg
import asyncio

async def main():
conn = await asyncpg.connect(os.environ["DATABASE_URI"])
async with conn.transaction():
await conn.execute("-- hello")

if __name__ == "__main__":
asyncio.run(main())
```

Is this:
```
Traceback (most recent call last):
File "/home/msa/dev/sandbox/pgtesting/hello.py", line 13, in
asyncio.run(main())
~~~~~~~~~~~^^^^^^^^
File "/home/msa/.local/share/uv/python/cpython-3.13.0-linux-x86_64-gnu/lib/python3.13/asyncio/runners.py", line 194, in run
return runner.run(main)
~~~~~~~~~~^^^^^^
File "/home/msa/.local/share/uv/python/cpython-3.13.0-linux-x86_64-gnu/lib/python3.13/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "/home/msa/.local/share/uv/python/cpython-3.13.0-linux-x86_64-gnu/lib/python3.13/asyncio/base_events.py", line 721, in run_until_complete
return future.result()
~~~~~~~~~~~~~^^
File "/home/msa/dev/sandbox/pgtesting/hello.py", line 9, in main
await conn.execute("-- hello")
File "/home/msa/dev/sandbox/pgtesting/.venv/lib/python3.13/site-packages/asyncpg/connection.py", line 349, in execute
result = await self._protocol.query(query, timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "asyncpg/protocol/protocol.pyx", line 375, in query
File "asyncpg/protocol/protocol.pyx", line 888, in asyncpg.protocol.protocol.BaseProtocol._dispatch_result
File "asyncpg/protocol/protocol.pyx", line 815, in asyncpg.protocol.protocol.BaseProtocol._on_result__simple_query
AttributeError: 'NoneType' object has no attribute 'decode'
```
Setup is just
```
mkdir hello
cd hello
uv init .
uv add asyncpg
export DATABUTTON_URI="something"
uv run hello.py # above example
```

Start with asyncpg/connection.py at Connection.execute and follow the protocol query path shown in asyncpg/protocol/protocol.pyx, especially _on_result__simple_query. Reproduce the comment-only query, then add or update coverage so it completes successfully without the NoneType decode error and preserves normal results for nonempty queries.

Written by the indexing model from the issue text.