Bugfix for Install-PSResource Null pointer when package is present only in upstream feed in ADO

[anamnavi]

PR Summary

Install-PSResource is throwing a null pointer exception when attempting to install a package from ADO V3 feed when the package isn't present in the main feed but was found in the upstream feed. The upstream feed requires permissions and ADO will report this error, but before it can be reported we check the value of a variable that will be null.

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