Optimization for DynamicCache.crop() with zero max_length
Author: ddz5431
Pull request: yes

# What does this PR do?
This PR ensures that DynamicCache.crop() does not modify the cache when max_length is set to zero.

Previously, calling crop(0) resulted in unnecessary operations, even though no cropping was required.
This fix improves efficiency and prevents unintended modifications to key_cache and value_cache.

### 🔹 Key Changes:
- Added an **early return** in `crop()` if `max_length == 0` to **prevent unnecessary operations**.
- Ensures that `key_cache` and `value_cache` remain unchanged when cropping is not needed.

```
# Do not crop anything if it is zero
if max_length == 0:
    return
```

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