[importer] Incorrect Warning for tables starting with #

Steps to reproduce:
1. Go to importer.
2. Select "File" and select a csv file.
3. Click on Next.
4. Select "Table" option from the destination type dropdown.
5. First select an existing table. The "Existing..." warning will come.
6. Now replace that content with come invalid text eg. "#$@%#$#^$".
7. Both "Existing..." and "Invalid..." warnings appear.
Expected: Only "Invalid..." warning should come.