Having issues logging onto servers when using anything below 1.8

I was trying to log onto a friends server using 1.7.9 but every time i tried to do so, this resulted in my minecraft crashing but i have had this problem before when trying onto server after switching from 1.8 to 1.7.9.

Before i attempted to log onto the server, i had closed the main minecraft window and opened my profile within the launcher and switched it to 1.7.9 from 1.8 and clicked save profile - the game opened successfully but when i clicked join server for my friends server , it crashed.