jquery autocomplete Cannot read property 'replace' of undefined

$('#tags').autocomplete({
    params: {search_type:$('#search-type').val()},
    minChars: 2,
    appendTo: $(".cash-collection-select"),
    serviceUrl: '/admin/journals/search_roles',
    onSelect: function (suggestion) {
      $("#q").val(suggestion.data);
      console.log(suggestion.data)
      alert("You selected: ' + suggestion.value + ', ' + suggestion.data")
    },
    onSearchStart: function(query) {
    console.log("query: "+query)
    },
    onSearchComplete: function (query, suggestions) {
      console.log(suggestions.data)
    }
  });

I am getting the error Cannot read property 'replace' of undefined. My response from the rails action is coming in json format

suggestions = User.where("email LIKE ?","#{params[:query]}%")
    message = {:query => "Unit", :suggestions => suggestions}
    render :json => message

this is my input #tags

<input class="search-emails" type="email" id="tags" placeholder="Search by email.." />