Save-PSResource: Improve error message when passing bad package name that looks like a filename

[helpimnotdrowning]

Summary of the new feature / enhancement

I was mistakenly running the command

Save-PSResource ./Sisk.HttpServer -Path ./test`

and getting confused when I would get the error

Save-PSResource: Object reference not set to an instance of an object.

I was thinking that this was a bug where Save-PSResource was not able to find the path I was passing, but only after lots of "troubleshooting" did I realize that I prepended my package name with "./" - the error message is not helpful.

This specific error only seems to occur when the package name looks like a path, ex. ./PackageName or /PackageName. It is not due to some invalid characters in the package name, running Save-PSResource Sisk./HttpServer correctly tries to search all of my repositories before writing

Save-PSResource: Package(s) 'Sisk./HttpServer' could not be installed from registered repositories 'NuGetGallery, PSGallery'.

Additionally, with this error it stops searching after the first repository.

---

With -Verbose:

Save-PSResource /Sisk.HttpServer -Version 1.5.2 -Path . -TrustRepository -Verbose -Repository NuGetGallery 
VERBOSE: Attempting to search for packages in 'NuGetGallery'
WARNING: Installing dependencies is not currently supported for V3 server protocol repositories. The package will be installed without installing dependencies.
VERBOSE: Performing the operation "Save-PSResource" on target "Package to save: 'Sisk.HttpServer', version: '1.5.2'".
VERBOSE: Performing the operation "Save-PSResource" on target "Package to install: 'Sisk.HttpServer', version: '1.5.2'".
VERBOSE: This resource is not a PowerShell package and will be installed to the modules path: .
Save-PSResource: Object reference not set to an instance of an object.
VERBOSE: Attempting to delete '/tmp/35ba3d33-4c54-4f1e-a56e-9d38b6a0788d'
VERBOSE: Successfully deleted '/tmp/35ba3d33-4c54-4f1e-a56e-9d38b6a0788d'
Save-PSResource: Object reference not set to an instance of an object.

Proposed technical implementation details (optional)

No response