Check convert available by thumbnails #1357

app/models/dmsf_file.rb

@@ -488,6 +488,10 @@ class DmsfFile < ActiveRecord::Base
     (image? || pdf? || video? || html?) ? 'inline' : 'attachment'
   end
 
+  def thumbnailable?
+    image? && Redmine::Thumbnail.convert_available?
+  end
+
   def preview(limit)
     result = +'No preview available'
     if text?

app/views/dmsf_files/_thumbnails.html.erb

@@ -22,7 +22,7 @@
 
 <% # Thumbnails %>
 <% if defined?(thumbnails) && thumbnails %>
-    <% images = links.map{ |x| x[0] }.select(&:image?) %>
+    <% images = links.map{ |x| x[0] }.select(&:thumbnailable?) %>
     <% if images.any? %>
         <% if link_to # Redmine classic %>
           <div class="thumbnails">