[Mono.Addins] Don't wipe out all the loaded assemblies when unloading an addin
[Mono.Addins] Don't wipe out all the loaded assemblies when unloading an addin

Actually copy the loadedAssemblies dictionary instead of just creating a new empty dictionary.

Fixes BXC #14845 - Getting 'Error retrieving update information' in Check for Update window if user disable any option in Add-in Manager->MobileDevelopment

mono/mono-addins,mono/mono-addins