Unevaluable formulas return nil (instead of throwing error)

Filter formula errors are shown in filter view

app/views/ingredients/_filters.html.erb

@@ -1,5 +1,7 @@
 <fieldset id="filters" class="collapsible">
   <legend onclick="toggleFieldset(this);"><%= l(:label_filter_plural) %></legend>
+  <%= error_messages_for @formula_q %>
+
   <%= form_tag url, id: 'filters_form', method: :get, remote: true do %>
   <table class="filter">
     <tr>

app/views/ingredients/_list.html.erb

@@ -1,4 +1,7 @@
 <% if @ingredients.any? { |i| i.persisted? } %>
+  <%= render :partial => 'ingredients/filters',
+    :locals => {:url => filter_project_ingredients_path(@project)} %>
+
   <table class="list">
     <thead>
       <tr>

app/views/ingredients/_list_nutrients.html.erb

@@ -1,4 +1,7 @@
 <% if @nutrients.any? %>
+  <%= render :partial => 'ingredients/filters',
+    :locals => {:url => filter_nutrients_project_ingredients_path(@project)} %>
+
   <%= render :partial => 'ingredients/options' %>
 
   <table class="nutrients list odd-even">

app/views/ingredients/index.html.erb

@@ -13,8 +13,6 @@
 <%= render :partial => 'ingredients/form' %>
 
 <h2><%= t ".heading" %></h2>
-<%= render :partial => 'ingredients/filters',
-  :locals => {:url => filter_project_ingredients_path(@project)} %>
 <div id='ingredients'>
   <%= render :partial => 'ingredients/list' %>
 </div>

app/views/ingredients/nutrients.html.erb

@@ -13,8 +13,6 @@
 <%= render :partial => 'ingredients/form' %>
 
 <h2><%= t ".heading" %></h2>
-<%= render :partial => 'ingredients/filters',
-  :locals => {:url => filter_nutrients_project_ingredients_path(@project)} %>
 <div id='nutrients'>
   <%= render :partial => 'ingredients/list_nutrients' %>
 </div>