RTK GPS Inject: big scary message re semaphore timeout

No idea what was behind this issue but we shouldn't ever display these big scary messages which seem to come from unhandled exceptions. This particular message says "semaphore timeout".

The issue reports a raw “semaphore timeout” message during RTK GPS Inject and includes a screenshot, but names no source file or test. Start by reproducing RTK GPS Inject and tracing where this message reaches the user; done means the timeout is handled with an appropriate user-facing result instead of an unhandled-exception message.

Written by the indexing model from the issue text.