Let task continue dispaching while meeting unexpected doc formats (#199)

### 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._

Issue link:#[[Link the issue
here](https://github.com/infiniflow/ragflow/issues/198)]

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Breaking Change (fix or feature that could cause existing
functionality not to work as expected)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Test cases
- [ ] Python SDK impacted, Need to update PyPI
- [ ] Other (please describe):

rag/svr/task_broker.py

@@ -73,7 +73,7 @@ def dispatch():
                 for t in tsks:
                     TaskService.delete_by_id(t.id)
         except Exception as e:
-            cron_logger.error("delete task exception:" + str(e))
+            cron_logger.exception(e)
 
         def new_task():
             nonlocal r
@@ -83,6 +83,7 @@ def dispatch():
             }
 
         tsks = []
+        try:
             if r["type"] == FileType.PDF.value:
                 do_layout = r["parser_config"].get("layout_recognize", True)
                 pages = PdfParser.total_page_number(
@@ -121,6 +122,9 @@ def dispatch():
 
             bulk_insert_into_db(Task, tsks, True)
             set_dispatching(r["id"])
+        except Exception as e:
+            cron_logger.exception(e)
+
         tmf.write(str(r["update_time"]) + "\n")
     tmf.close()