Fixed: If/Else branching for UTM Campaign (Last Attribution)

Users had reported inconsistent behavior - the custom value picker would fall back to the campaign variable when UTM Campaign (Last Attribution) was empty, but If/Else conditions would not. This caused workflows to branch unexpectedly.

If/Else conditions now correctly apply the same fallback logic as the custom value picker for UTM Campaign (Last Attribution).

If UTM Campaign (Last Attribution) is empty, If/Else conditions will now automatically use the campaign variable as a fallback, ensuring consistent behavior across both areas.