Actually test SetConfigSearchPaths for empty array.

I lied when I said I tested this 2 commits earlier.
Make sure
SetConfigSearchPaths(level, string[] { })
behaves the same as
SetConfigSearchPaths(level, null)

Author: Ryan Roden-Corrent

LibGit2Sharp.Tests/ConfigurationFixture.cs

@@ -480,6 +480,7 @@ public void CanResetSearchPaths()
                 () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global),
                 () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null),
                 () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, string.Empty),
+                () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, new string[] { }),
             };
 
             // record the default search path