Omit space after omitted stream indicator

[kevgo]

When disabling the stream indicator, e.g. (o) or (e), it prints an extra space:

app1 : output

This PR changes it to this:

app1: output

I can't verify that this works due to lack of end-to-end tests, and this being a "stringly-typed" problem where Rust's strong typing doesn't help.

[allonsy]

@kevgo confirmed that this works. I ran it by using cargo run --example main_stdout. Remember that the examples directory contains a bunch of examples with a few different use cases

[kevgo]

Ah, I forgot that I can run the examples. This is so useful. Thanks for the reminder!