Repeated program response to view command when user input author does not exist in the catalog

[philip1304]

When inputting the view command using an author that does not exist within the program's catalog, the program repeats a part of its response twice.

Steps to reproduce:

• Use the view command to view an author that does not exist within the program's catalog.
• The program will reply with "Author does not exist! \n Author [] does not exist!"