[lipstick] Fix crash on close regression
[lipstick] Fix crash on close regression

6c6a924 reintroduced a segfault when closing lipstick. m_instance
was used after being reset to NULL.

matthewvogt/lipstick,matthewvogt/lipstick,sletta/lipstick,rainisto/lipstick,pvuorela/lipstick,rainisto/lipstick,giucam/lipstick,rainisto/lipstick,giucam/lipstick,matthewvogt/lipstick,sletta/lipstick,pvuorela/lipstick,giucam/lipstick,pvuorela/lipstick,sletta/lipstick