Support case of passing a nil exclusions list

So that both omitting the key entirely, and providing it but with a nil value, are both the same as using an empty exclusion list

Author: AliSoftware

lib/fastlane/plugin/wpmreleasetoolkit/helper/android/android_localize_helper.rb

@@ -24,7 +24,7 @@ def self.skip_string_by_tag(string_line)
 
         # Checks if string_name is in the excluesion list
         def self.skip_string_by_exclusion_list(library, string_name)
-          return false unless library.key?(:exclusions)
+          return false if library[:exclusions].nil?
 
           skip = library[:exclusions].include?(string_name)
           if skip