CalculateCoverage: Fix file not foundexception

[sbalant]

Check if the file HitsFilePath exists

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I have the same issue as #8
This simple check fix my problem

[coveralls]

Pull Request Test Coverage Report for Build #21

• 0 of 0 (NaN%) changed or added relevant lines in 0 files are covered.
• 7 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.04%) to 83.106%

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Files with Coverage Reduction	New Missed Lines	%
/src/coverlet.core/Coverage.cs	7	35.71%

Totals
Change from base Build #18:	-0.04%
Covered Lines:	305
Relevant Lines:	367

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💛 - Coveralls

[tonerdo]

Hi @sbalant, thanks for your contribution. I have some thoughts:

This approach just ignores the problem and it's not obvious to the user that something went wrong. A better approach will be to figure out why that error is even being thrown in the first place and try to prevent that. Possibly the file isn't being created in the first place? (https://github.com/tonerdo/coverlet/blob/master/src/coverlet.core/CoverageTracker.cs#L31)

[tonerdo]

@sbalant on second thought I'll have this PR now, that line should fix things when paired with #14. Before I merge though I notice your commits are not connected to your profile and as a result your contributions won't reflect. Are you fine with this?

[sbalant]

No problem ;)

[StillLearnin]

Any idea when this will be released to Nuget. I'm hitting this issue also.

[tonerdo]

@StillLearnin new NuGet package before Monday

[StillLearnin]

Splendid! Thanks!