String can be empty so return early if so

de4dot.code/renamer/TypeNames.cs

@@ -127,6 +127,8 @@ namespace de4dot.code.renamer {
 		}
 
 		protected static string upperFirst(string s) {
+			if (string.IsNullOrEmpty(s))
+				return string.Empty;
 			return s.Substring(0, 1).ToUpperInvariant() + s.Substring(1);
 		}
 	}

dot10

@@ -1 +1 @@
-Subproject commit d7ccb50d4ea85a48c05132dff8ae1e38c4dcbba2
+Subproject commit 47d3c156d6b725cc7d020dfcd8b17a025205985f