### What problem does this PR solve?

When parsing pptx files, some shapes do not contain the `shape_type`
attribute, which causes the original code to throw an exception during
extraction, leading to failure in content extraction. This optimization
introduces handling logic for such anomalous shapes, providing a safer
and more robust processing mechanism.

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [x] Refactoring
- [x] Performance Improvement
- [ ] Other (please describe):