Set-Stat errors
I'm now getting these errors after the 331cfc8 update:

```
Exchange rates: 1 BTC = USD 6662.98 = ETH 12.83944277
Cannot convert value "NaN" to type "System.Decimal". Error: "Value was either too large or too small for a Decimal."
At C:\MultiP00Lminer\Include.psm1:209 char:5
+     [PSCustomObject]@{
+     ~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : InvalidArgument: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvalidCastIConvertible
```

And then:

```
Compare-Object : Cannot bind argument to parameter 'DifferenceObject' because it is null.
At C:\MultiP00Lminer\MultiPoolMiner.ps1:350 char:257
+ ... SObject.Properties.Name $_.HashRates.PSObject.Properties.Name | Where ...
+                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : InvalidData: (:) [Compare-Object], ParameterBindingValidationException
+ FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Microsoft.PowerShell.Commands.CompareObjectCommand
```

[MultiPoolMiner_2018-06-14_15-16-40.txt](https://github.com/MultiPoolMiner/MultiPoolMiner/files/2104215/MultiPoolMiner_2018-06-14_15-16-40.txt)
[MultiPoolMiner_2018-06-14.txt](https://github.com/MultiPoolMiner/MultiPoolMiner/files/2104216/MultiPoolMiner_2018-06-14.txt)
