https://github.com/infiniflow/ragflow/issues/3651
### What problem does this PR solve?
_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve?
fix: display specific error message when previewing file error #868
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve?
feat: delete the added model #503
feat: display an error message when the requested file fails to parse
#684
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
