VM: initialize the ctx member in the construction
VM: initialize the ctx member in the construction

To make valgrind happy because it complains that it is uninitialized.

factor/factor,bpollack/factor,mrjbq7/factor,AlexIljin/factor,factor/factor,bpollack/factor,bpollack/factor,bjourne/factor,bjourne/factor,bpollack/factor,mrjbq7/factor,AlexIljin/factor,tgunr/factor,factor/factor,AlexIljin/factor,factor/factor,mrjbq7/factor,tgunr/factor,tgunr/factor,mrjbq7/factor,AlexIljin/factor,factor/factor,bpollack/factor,tgunr/factor,mrjbq7/factor,bpollack/factor,bjourne/factor,AlexIljin/factor,bjourne/factor,tgunr/factor,bpollack/factor,bjourne/factor,bjourne/factor,factor/factor,mrjbq7/factor,AlexIljin/factor,bjourne/factor,AlexIljin/factor,tgunr/factor