Throw when putting an invalid author name

[muratg]

From @Praburaj on August 21, 2014 20:39

This is a negative case, but just trying to cover scenarios.

Create an app and put the authors value as null like below

{
    "authors": [ null ]
}

Try doing a kpm build. Package is successfully generated. But when opening the package in nuget package explorer i see this error:

Copied from original issue: aspnet/dnx#560

[muratg]

From @StefH on February 4, 2015 19:3

Same error occurs when using empty string or empty strings.

{
    "authors": [ "" ]
}

or

{
    "authors": [ "", "" ]
}

[TheRealPiotrP]

kpm has been deprecated.