fix(opts): Adding check to prevent calls on nil wherer or joiner

[Jacobbrewer1]

Describe your changes

This pull request includes changes to the joiner.go and wherer.go files to improve the robustness of the appendJoin and appendWhere functions by adding nil checks.

Improvements to function robustness:

• joiner.go: Added a nil check for the Joiner interface in the appendJoin function to prevent potential nil pointer dereferences.
• wherer.go: Added a nil check for the Wherer interface in the appendWhere function to prevent potential nil pointer dereferences.