Make sure we don't crash when we get a null string

Author: larsbrubaker

GLFW.NET/Util.cs

@@ -19,12 +19,17 @@ internal static class Util
         // ReSharper disable once InconsistentNaming
         public static string PtrToStringUTF8(IntPtr ptr)
         {
-            var length = 0;
-            while (Marshal.ReadByte(ptr, length) != 0)
-                length++;
-            var buffer = new byte[length];
-            Marshal.Copy(ptr, buffer, 0, length);
-            return Encoding.UTF8.GetString(buffer);
+            if (ptr != IntPtr.Zero)
+            {
+                var length = 0;
+                while (Marshal.ReadByte(ptr, length) != 0)
+                    length++;
+                var buffer = new byte[length];
+                Marshal.Copy(ptr, buffer, 0, length);
+                return Encoding.UTF8.GetString(buffer);
+            }
+
+            return "";
         }
 
         #endregion