Fix Inspector message for the case when the simulator is not launched at all

[JoeSSS]

Launcher tries to detect launched device and compare it to iPhone 6,7,8, when the result is empty it will say:

We're sorry, but "Element Inspector" supports only iPhone 6, iPhone 7 or iPhone 8 devices.

Please choose one of the supported devices from "Test Runner" menu and click "Start Simulator" button being back to "Element Inspector".

But when there is no launched simulator, it will say the same. An this is not quite informative.

[BasThomas]

How is this broken right now? What is the message currently, and what would be the expected message?