Displaying errors for uncomputable formulas in nutrients view

app/helpers/body_trackers_helper.rb

@@ -1,6 +1,13 @@
 module BodyTrackersHelper
   def format_value(value)
     amount, unitname = value
-    amount.nil? ? '-' : "#{amount} [#{unitname || '-'}]"
+    case
+    when amount.nil?
+      '-'
+    when amount.nan?
+      '?'
+    else
+      "#{amount} [#{unitname || '-'}]"
+    end
   end
 end

app/models/formula.rb

@@ -30,9 +30,6 @@ class Formula < ActiveRecord::Base
       args << get_binding(quantities, args, length).eval(code)
     end
     args.last.map { |v| [v, nil] }
-  rescue Exception => e
-    puts e.message
-    [[nil, nil]] * length
   end
 
   private

app/views/ingredients/_nutrients.html.erb

@@ -4,6 +4,8 @@
 <% if @ingredients.any? %>
   <%= render partial: 'ingredients/options' %>
 
+  <%= error_messages_for *@quantities.map { |q| q.formula } %>
+
   <table class="nutrients list odd-even">
     <thead>
       <tr>