fix errors if no csv data or incorrect last group call specified

app/controllers/feed_controller.rb

@@ -104,8 +104,11 @@ class FeedController < ApplicationController
     # put feeds in correct order (oldest to most recent)
     last_feeds.reverse!
 
+    # check if the correct param is present by getting the param name from arg, e.g.: 'median' from 'medians'
+    correct_params_present = params[arg.chop.to_sym].present?
+
     feeds_into = self.method("feeds_into_#{arg}")
-    feed = feeds_into.call(last_feeds, params).last if last_feeds.length > 0
+    feed = feeds_into.call(last_feeds, params).last if last_feeds.length > 0 && correct_params_present
     create_group_result(feed)
   end
 

app/helpers/feed_helper.rb

@@ -272,6 +272,7 @@ module FeedHelper
 
   # slice feed into medians
   def feeds_into_medians(feeds, params)
+
     # convert timescale (minutes) into seconds
     seconds = params[:median].to_i * 60
     # get floored time ranges
@@ -355,7 +356,7 @@ module FeedHelper
   # checks for valid timescale
   def timeparam_valid?(timeparam)
     valid_minutes = [10, 15, 20, 30, 60, 240, 720, 1440]
-    if timeparam and valid_minutes.include?(timeparam.to_i)
+    if timeparam.present? && valid_minutes.include?(timeparam.to_i)
       return true
     else
       return false

app/views/feed/show.csv.erb

@@ -1,2 +1,2 @@
-<% if @success %><%= CSV.generate_line @csv_headers %><% row = [] %><% @csv_headers.each do |attr| %><% row.push(@feed.send(attr)) %><% end %><%= CSV.generate_line row %><% else %>-1<% end %>
+<% if @success && @csv_headers.present? %><%= CSV.generate_line @csv_headers %><% row = [] %><% @csv_headers.each do |attr| %><% row.push(@feed.send(attr)) %><% end %><%= CSV.generate_line row %><% else %>-1<% end %>