Explain why address is not found

[behas]

It happens quite frequently that users enter addresses that were never involved in transactions. When they enter the address in GraphSense, they don't find anything. We should show the user some message saying that the address has probably never been used.

[myrho]

A respective message is already poping up, when the user presses the search button or enter. However, on autocompletion no message is shown. Should we add one here too?