networks-inject reports success even if it couldn't inject addresse

From [discord](https://discord.com/channels/477106835862716416/477390900830535680/727252704317145220)

> also I found a clear bug that if you make empty build/contracts and run yarn run networks-inject it will say that all is fine, but do nothing

If we cannot inject the addresses into the contracts we should fail the script and let the user know.

Start at the networks-inject entry point invoked by yarn and reproduce the issue with an empty build/contracts directory. Trace how unsuccessful address injection is handled. Done means the command reports failure and clearly tells the user when addresses could not be injected, rather than reporting success.

Written by the indexing model from the issue text.