## Reasoning Steps for Generating the Patch:

### Step 1: Root Cause Analysis

1. **Data Source:** The variable `pps_id` is read from a bitstream (`bs`) using `gf_bs_read_ue_log`. This function suggests that `pps_id` is expected to be an unsigned integer.

2. **Vulnerable Access:** The code attempts to access an element in the `hevc->pps` array using `pps_id` as the index.

3. **Missing Check:** The existing code only checks if `pps_id` is greater than or equal to 64. This implies that the `hevc->pps` array might have a size of 64.

4. **Potential Vulnerability:** The vulnerability arises if `pps_id` is negative. When a negative value is used as an array index in C, it leads to out-of-bounds access. This can cause a crash or potentially allow an attacker to read from or write to arbitrary memory locations. 

### Step 2: Fixing Strategy

1. **Add Negative Index Check:** To prevent the out-of-bounds access, we need to ensure that `pps_id` is not negative. This can be achieved by adding an additional check `(pps_id < 0)` before accessing the `hevc->pps` array.

### Conclusion

The patched code adds an essential check for negative values of `pps_id`. This prevents the potential out-of-bounds array access vulnerability (CWE-125) that existed in the original code. The patch ensures that only valid indices within the bounds of the `hevc->pps` array are used, improving the security and robustness of the code. 
