Bug 18095: Batch item modification: Better message if no item is modified

Bug 18095: Batch item modification: Better message if no item is modified

If no item is modified, the result page of Batch item modification says:
"item(s) modified (with fields modified)."
The message should be: "No items modified"

To reproduce:
- Go to Tools -> Batch item modification
- Put a barcode in and click Continue
- Do not make any changes and/or deselect all item(s)
- Click "Save"
=> Result message reads: "item(s) modified (with fields modified)."

To test:
- Apply patch
- Repeat steps above
- Verify that message makes sense.

NOTE: Also tested positive case with actual field change.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Mason James <mtj@kohaaloha.com>