Don't update a nil value

Author: kpaulisse

lib/octocatalog-diff/catalog-util/builddir.rb

@@ -284,7 +284,7 @@ def install_ssl(logger, options)
       # @param obj [Hash] Parsed hiera.yaml file
       def update_hiera_config_v3(logger, options, obj)
         ([obj[:backends]].flatten || %w(yaml json)).each do |key|
-          next unless obj.key?(key.to_sym)
+          next unless obj.key?(key.to_sym) && !obj[key.to_sym][:datadir].nil?
           obj[key.to_sym][:datadir] = hiera_munge(options, obj[key.to_sym][:datadir])
 
           # Make sure the directory exists. If not, log a warning. This is *probably* a setup error, but we don't