Fix #10446 - Resolve issue preventing link creation in Security Groups sub-panels

Description

This commit addresses an issue where related custom module items couldn't be selected via sub-panels. The problem occurred when the bean with the relationship link property was empty and not an instance of Link2.

The root cause was identified within the Link2 class's add() function, specifically when the getSide() method returns 'RHS'. This situation arose when either the 'RHS' or 'LHS' was set to 'SecurityGroup' in the M2MRelationship add() function.

Motivation and Context

This will fix a bug where you are unable to make selections using Security Groups sub-panels.

How To Test This

1.Open the Security groups module ui 2.Use the 'Create' button's 'Select' option on any custom module 3.In the pop-up window select a single or multiple options using the checkbox 4.Click 'Select'

Types of changes

[X] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

Final checklist

[X] My code follows the code style of this project found here.
[ ] My change requires a change to the documentation.
[X] I have read the How to Contribute guidelines.

salesagility / SuiteCRM