Silly null references

src/resharper-nuget/NuGetApi.cs

@@ -58,9 +58,9 @@ private bool IsNuGetAvailable
             get { return vsPackageInstallerServices != null && vsPackageInstaller != null; }
         }
 
-        public bool AreAnyAssemblyFilesNuGetPackages(IEnumerable<FileSystemPath> fileLocations)
+        public bool AreAnyAssemblyFilesNuGetPackages(IList<FileSystemPath> fileLocations)
         {
-            if (!IsNuGetAvailable)
+            if (!IsNuGetAvailable || fileLocations.Count == 0)
                 return false;
 
             // We're talking to NuGet via COM. Make sure we're on the UI thread
@@ -73,9 +73,9 @@ public bool AreAnyAssemblyFilesNuGetPackages(IEnumerable<FileSystemPath> fileLoc
             return hasPackageAssembly;
         }
 
-        public string InstallNuGetPackageFromAssemblyFiles(IEnumerable<FileSystemPath> assemblyLocations, IProject project)
+        public string InstallNuGetPackageFromAssemblyFiles(IList<FileSystemPath> assemblyLocations, IProject project)
         {
-            if (!IsNuGetAvailable)
+            if (!IsNuGetAvailable || assemblyLocations.Count == 0)
                 return null;
 
             string installedAssembly = null;

src/resharper-nuget/NuGetModuleReferencer.cs

@@ -82,7 +82,7 @@ private static IList<FileSystemPath> GetAllAssemblyLocations(IPsiModule psiModul
         {
             var projectModelAssembly = psiModule.ContainingProjectModule as IAssembly;
             if (projectModelAssembly == null)
-                return null;
+                return EmptyList<FileSystemPath>.InstanceList;
 
             // ReSharper maintains a list of unique assemblies, and each assembly keeps a track of
             // all of the file copies of itself that the solution knows about. This list of file