[Bug] appendonlyam_handler.c:1790:25: error: ‘segfile_count’ may be used uninitialized

### Apache Cloudberry version

main branch commit: 644b4e307380954e986f048d0a7910a3063e524e

### What happened

```shell
appendonlyam_handler.c: In function ‘appendonly_index_build_range_scan’:
appendonlyam_handler.c:1790:25: error: ‘segfile_count’ may be used uninitialized [-Werror=maybe-uninitialized]
1790 | FreeAllSegFileInfo(seginfo, segfile_count);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
aocsam_handler.c: In function ‘aoco_index_build_range_scan’:
aocsam_handler.c:1952:25: error: ‘segfile_count’ may be used uninitialized [-Werror=maybe-uninitialized]
1952 | FreeAllAOCSSegFileInfo(seginfo, segfile_count);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

```

### What you think should happen instead

_No response_

### How to reproduce

config, make

### Operating System

Ubuntu

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes, I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/cloudberry/blob/main/CODE_OF_CONDUCT.md).

Start by reproducing the warning with `config, make`, then inspect `appendonlyam_handler.c` around line 1790 and `aocsam_handler.c` around line 1952. Confirm how `segfile_count` is handled before each `FreeAllSegFileInfo` and `FreeAllAOCSSegFileInfo` call; done means the Ubuntu build completes without the `maybe-uninitialized` errors.

Written by the indexing model from the issue text.