Added not defined ABSPATH check to prevent direct file access

Some files could be accessed directly and could cause a direct files access.

This vulnerability affects the following application versions:

• All in One SEO Pack 4.0.6
• All in One SEO Pack 4.0.7
• All in One SEO Pack 4.0.8
• All in One SEO Pack 4.0.9
• All in One SEO Pack 4.0.10
• All in One SEO Pack 4.0.12
• All in One SEO Pack 4.0.15