dylan 5aae73c230
Make error messages during PPT processing clearer. (#6980)
### What problem does this PR solve?

Sometimes a slide may trigger a Proxy error (ArgumentException:
Parameter is not valid) due to issues in the original file, and this
error message can be confusing for users.

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [x] Other (please describe):
2025-04-14 10:10:20 +08:00
..
2025-03-26 15:34:42 +08:00
2025-01-21 20:52:28 +08:00