Threshold not fail when no module

[daveMueller]

closes #1083

[daveMueller]

An output like the following

+--------+------+--------+--------+
| Module | Line | Branch | Method |
+--------+------+--------+--------+

+---------+------+--------+--------+
|         | Line | Branch | Method |
+---------+------+--------+--------+
| Total   | 100% | 100%   | 100%   |
+---------+------+--------+--------+
| Average | NaN% | NaN%   | NaN%   |
+---------+------+--------+--------+

currently only happens when for what ever reason the Modules are empty. In the first part of the summary there is no entry because no Module exists in the result. That is also the reason why Average is NaN because there is a division by zero (Modules.Count=0).
As the issue already stated a coverage of 100% is the wrong value to return in this case.

There are two solution I can think of. One would throw an exception. Something like "No coverage could be calculated because the result doesn't contain any modules." However this might break some CI pipelines just because coverage has an issue.

The other solution would be to return a coverage of 0 when this happens. This is what I prepared in this PR. But personally I'm a bit divided about this. What do you think, @MarcoRossignoli @martincostello ?

[martincostello]

Yeah I think 0% is better, as then the coverage threshold will take effect if it's configured and fail the build that way.

[MarcoRossignoli]

I agree with Martin, go for 0% and fail if there is a threshold check.

Thx Dave.

[MarcoRossignoli]

LGTM

[MarcoRossignoli]

@daveMueller remember to update the changelog thx a lot!