Keywords plugin for Habari

Notice: Undefined offset:  1 in user/plugins/keywords/keywords.plugin.php line 196

user/plugins/keywords/keywords.plugin.php line 69:
  Keywords->extract_keywords( …1 arg… )
[core] line 0:
  Keywords->filter_final_output( …1 arg… )
system/classes/plugins.php line 126:
  call_user_func_array( …1 args… )
system/index.php line 200:
  Plugins::filter( …1 args… )
index.php line 21:
  require( …1 arg… )