lancedb-fix-phi-2404 (#1787)

## Description

Lancedb insert bug fix 

Fixes #1780

## Type of change

Please check the options that are relevant:

- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] Model update
- [ ] Infrastructure change

## Checklist

- [ ] My code follows Phidata's style guidelines and best practices
- [ ] I have performed a self-review of my code
- [ ] I have added docstrings and comments for complex logic
- [ ] My changes generate no new warnings or errors
- [ ] I have added cookbook examples for my new addition (if needed)
- [ ] I have updated requirements.txt/pyproject.toml (if needed)
- [ ] I have verified my changes in a clean environment

## Additional Notes

Include any deployment notes, performance implications, or other
relevant information:

phi/vectordb/lancedb/lance_db.py

@@ -128,7 +128,7 @@ def doc_exists(self, document: Document) -> bool:
         Args:
             document (Document): Document to validate
         """
-        if self.table:
+        if self.table is not None:
             cleaned_content = document.content.replace("\x00", "\ufffd")
             doc_id = md5(cleaned_content.encode()).hexdigest()
             result = self.table.search().where(f"{self._id}='{doc_id}'").to_arrow()
@@ -164,11 +164,16 @@ def insert(self, documents: List[Document], filters: Optional[Dict[str, Any]] =
             )
             logger.debug(f"Inserted document: {document.name} ({document.meta_data})")
 
-        if self.table:
-            self.table.add(data)
-            logger.debug(f"Upsert {len(data)} documents")
-        else:
+        if self.table is None:
             logger.error("Table not initialized. Please create the table first")
+            return
+
+        if not data:
+            logger.debug("No new data to insert")
+            return
+
+        self.table.add(data)
+        logger.debug(f"Inserted {len(data)} documents")
 
     def upsert(self, documents: List[Document], filters: Optional[Dict[str, Any]] = None) -> None:
         """