fix up erros on planting form

app/controllers/plantings_controller.rb

@@ -46,7 +46,9 @@ class PlantingsController < ApplicationController
 
     # using find_by_id here because it returns nil, unlike find
     @crop     = Crop.approved.find_by(id: params[:crop_id]) || Crop.new
-    @garden   = Garden.find_by(owner: current_member, id: params[:garden_id])
+    @planting.garden   = Garden.find_by(
+        owner: current_member,
+        id: params[:garden_id]) if params[:garden_id]
 
     respond_with @planting
   end

app/views/plantings/_form.html.haml

@@ -27,15 +27,11 @@
 
       .row
         .col-md-8
-          - if @garden.present?
-            %p Planted in #{link_to @garden, @garden}
-            = f.hidden_field :garden_id, value: @garden.id
-          - else
-            = f.collection_radio_buttons(:garden_id,
-              @planting.owner.gardens.active.order_by_name,
-              :id, :name, required: true,
-              label: 'Where did you plant it?')
-            = link_to "Add a garden.", new_garden_path
+          = f.collection_radio_buttons(:garden_id,
+            @planting.owner.gardens.active.order_by_name,
+            :id, :name, required: true,
+            label: 'Where did you plant it?')
+          = link_to "Add a garden.", new_garden_path
         .col-md-4
           = f.text_field :planted_at,
                      value: @planting.planted_at ? @planting.planted_at.to_s(:ymd) : '',