Book can be created with empty author

[mohamadalbasleh]

Description:
System allows saving a new book when the Author field is left blank, resulting in incomplete and unclear book records.
Steps to Reproduce:

1. Go to Add Book page.
2. Leave the Author field empty.
3. Fill remaining required fields (including Title) and click Save.
   Expected Result:
   Validation message “Author is required” is shown and the book is not saved.
   Actual Result:
   Book is saved with an empty/null author field.
   Severity: Medium
   Priority: P2
   Status: New
   Environment: Chrome 129, Windows 11
   Screenshot / Evidence: