Make sure we don't crash with file remote origin

Author: haacked

src/GitHub.Exports/Primitives/UriString.cs

@@ -125,6 +125,8 @@ bool ParseScpSyntax(string scpString)
         /// <returns></returns>
         public Uri ToRepositoryUrl()
         {
+            if (url != null && IsFileUri) return url;
+
             var scheme = url != null && IsHypertextTransferProtocol
                 ? url.Scheme
                 : Uri.UriSchemeHttps;

src/UnitTests/GitHub.Primitives/UriStringTests.cs

@@ -162,6 +162,7 @@ public void ReturnWhetherTheUriIsParseableByUri(string uriString, bool expected)
     public class TheToRepositoryUrlMethod
     {
         [Theory]
+        [InlineData("file:///C:/dev/exp/foo", "file:///C:/dev/exp/foo")]
         [InlineData("http://example.com/", "http://example.com/")]
         [InlineData("http://[email protected]/foo/bar", "http://example.com/foo/bar")]
         [InlineData("https://github.com/github/Windows", "https://github.com/github/Windows")]