avoid error in Docker uploading a datafile with no assays

added a dummy line to instantiate an Assay, which helps avoid an error later when attempting to access a method on an unmarshalled assay instance from the session. The error involved attempting to call super within a module, before the Assay class had yet been encountered for that process.

app/controllers/data_files_controller.rb

@@ -461,6 +461,11 @@ def rightfield_extraction_ajax
   def provide_metadata
     @data_file ||= session[:processed_datafile]
     @assay ||= session[:processed_assay]
+
+    #this perculiar line avoids a no method error when calling super later on, when there are no assays in the database
+    # this I believe is caused by accessing the unmarshalled @assay before the Assay class has been encountered. Adding this line
+    # avoids the error
+    Assay.new
     @warnings ||= session[:processing_warnings] || []
     @exception_message ||= session[:extraction_exception_message]
     @create_new_assay = !(@assay.title.blank? && @assay.description.blank?)