Catch Encoding::ConverterNotFoundError

Some binary format on Active Directory can raise "Encoding::ConverterNotFoundError".

Signed-off-by: Jason Franklin <franklin@equinux.com>

Author: Jason Franklin

lib/net/ber/core_ext/string.rb

@@ -32,6 +32,8 @@ def raw_utf8_encoded
         self.encode('UTF-8').force_encoding('ASCII-8BIT')
       rescue Encoding::UndefinedConversionError
         self
+      rescue Encoding::ConverterNotFoundError
+        return self
       end
     else
       self