fixing chuncks controller mime types validation

Signed-off-by: man13 <man13@inf.ufpr.br>

app/controllers/chunks_controller.rb

@@ -113,7 +113,9 @@ class ChunksController < ApplicationController
   end
 
   def valid_mime_type?
-    @learning_object.object_type.mime_types.map(&:extension).include? resumable_file_extension
+    mime_types = @learning_object.object_type.mime_types.map(&:extension)
+    return true if mime_types.empty?
+    mime_types.include? resumable_file_extension
   end
   # Never trust parameters from the scary internet, only allow the white list through.
   def chunks_params