Context not set if node type human readable name contains dash (-)

If the human readable name of a node type contains a dash, for example: 'news-item', the system name of the node type is 'news_item'. The path to add a node of that node type will be: /node/add/news-item. The og-context module assumes that the third item of the path is the node type system name which is incorrect (see line 379 of og_context.module). The subsequent call to og_get_group_audience_fields() will not return the fields for the node-type, thus the context is not set correctly. The system name of a node type can never contain a dash, so replacing any dashes by underscores is a solution.