Add null check to RemoteCollection

Author: asbjornu

src/GitVersion.LibGit2Sharp/Git/RemoteCollection.cs

@@ -1,11 +1,17 @@
+using GitVersion.Extensions;
+
 namespace GitVersion;
 
 internal sealed class RemoteCollection : IRemoteCollection
 {
     private readonly LibGit2Sharp.RemoteCollection innerCollection;
-    internal RemoteCollection(LibGit2Sharp.RemoteCollection collection) => this.innerCollection = collection;
 
-    public IEnumerator<IRemote> GetEnumerator() => this.innerCollection.Select(reference => new Remote(reference)).GetEnumerator();
+    internal RemoteCollection(LibGit2Sharp.RemoteCollection collection)
+        => this.innerCollection = collection.NotNull();
+
+    public IEnumerator<IRemote> GetEnumerator()
+        => this.innerCollection.Select(reference => new Remote(reference)).GetEnumerator();
+
     IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
 
     public IRemote? this[string name]
@@ -18,5 +24,7 @@ public IRemote? this[string name]
     }
 
     public void Remove(string remoteName) => this.innerCollection.Remove(remoteName);
-    public void Update(string remoteName, string refSpec) => this.innerCollection.Update(remoteName, r => r.FetchRefSpecs.Add(refSpec));
+
+    public void Update(string remoteName, string refSpec)
+        => this.innerCollection.Update(remoteName, r => r.FetchRefSpecs.Add(refSpec));
 }