Fix missing openContents.securityLvel error when unlocking keychain

I get this error when I try to unlock the keychain:

    /home/stayrad/Git/1pass/lib/contents.js:96
          return this.detail().openContents.securityLevel || 'SL5';
                                           ^
    TypeError: Cannot read property 'securityLevel' of undefined
        at Item.Contents.Item.Item.securityLevel (/home/stayrad/Git/1pass/lib/contents.js:96:40)
        at Database.search (/home/stayrad/Git/1pass/lib/database.js:46:32)
        at /home/stayrad/Git/1pass/lib/app.js:58:32
        at /home/stayrad/Git/1pass/lib/app.js:104:20
        at ChildProcess.<anonymous> (/home/stayrad/Git/1pass/lib/password_server.js:27:20)
        at ChildProcess.EventEmitter.emit (events.js:98:17)
        at handleMessage (child_process.js:318:12)
        at Pipe.channel.onread (child_process.js:339:9)

I haven't done much testing, but I'm guessing that one of the items in my keychain doesn't have the openContents property.

A simple fix would be to check that `@detail().openContents` exists before getting `@detail().openContents.securityLevel`.

I've run `make test` and it doesn't seem to cause any side effects.