use a default icon if no plant_part icon

app/helpers/icons_helper.rb

@@ -92,7 +92,7 @@ module IconsHelper
   end
 
   def plant_part_icon(name)
-    image_icon "plant_parts/#{name}" if Files.exists? Rails.root.join('app', 'assets', 'images', 'icons', "{name}.svg")
+    image_icon "plant_parts/#{name}" if File.exist? Rails.root.join('app', 'assets', 'images', 'icons', "{name}.svg")
     planting_icon
   end