panic: interface conversion: interface {} is nil, not bool

latest in master, compiled in yosemite:

(venv) users-iMac:bitmask-systray user1$ ./bitmask-systray --version
0.0.1-2-g909c059
(venv) users-iMac:bitmask-systray user1$ ./bitmask-systray 
panic: interface conversion: interface {} is nil, not bool

goroutine 9 [running]:
0xacab.org/leap/bitmask-systray/bitmask.(*Bitmask).VPNCheck(0xc4200f2e80, 0x0, 0x0, 0x0)
        /Users/user1/go/src/0xacab.org/leap/bitmask-systray/bitmask/vpn.go:55 +0x234
main.checkAndInstallHelpers(0xc4200f2e80, 0xc42000e2b8, 0x0, 0x0)
        /Users/user1/leap/bitmask-dev/pkg/bitmask-systray/main.go:86 +0x2f
main.checkAndStartBitmask(0xc4200f2e80, 0xc42000e2b8, 0xc42005e200)
        /Users/user1/leap/bitmask-dev/pkg/bitmask-systray/main.go:73 +0x3c
created by main.main
        /Users/user1/leap/bitmask-dev/pkg/bitmask-systray/main.go:67 +0x228