fix tempfile of chunks controller

app/controllers/v1/learning_objects/chunks_controller.rb

@@ -41,10 +41,12 @@ class V1::LearningObjects::ChunksController < ApplicationController
   ##
   # Move the temporary Sinatra upload to the chunk file location
   def save_file!
+    return nil unless chunks_params[:file].try(:tempfile).is_a? Tempfile
+
     # Ensure required paths exist
     FileUtils.mkpath(chunk_file_directory)
     # Move the temporary file upload to the temporary chunk file path
-    FileUtils.mv(params[:file][:tempfile], chunk_file_path, force: true)
+    FileUtils.mv(chunks_params[:file].tempfile, chunk_file_path, force: true)
   end
 
   ##
@@ -66,31 +68,31 @@ class V1::LearningObjects::ChunksController < ApplicationController
   def valid_mime_type?
     mime_types = @learning_object.object_type.mime_types.map(&:extension)
     return true if mime_types.empty?
-    mime_types.include? params[:flowFilename].split('.').last
+    mime_types.include? chunks_params[:flowFilename].split('.').last
   end
 
   ##
   # Determine if this is the last chunk based in parts count.
   def last_chunk?
-    Dir["#{chunk_file_directory}/#{params[:flowFilename]}.part*"].count == params[:flowTotalChunks].to_i
+    Dir["#{chunk_file_directory}/#{chunks_params[:flowFilename]}.part*"].count == chunks_params[:flowTotalChunks].to_i
   end
 
   ##
   # ./tmp/flow/abc-123/upload.txt.part1
   def chunk_file_path
-    File.join(chunk_file_directory, "#{params[:flowFilename]}.part#{params[:flowChunkNumber]}")
+    File.join(chunk_file_directory, "#{chunks_params[:flowFilename]}.part#{chunks_params[:flowChunkNumber]}")
   end
 
   ##
   # ./tmp/flow/abc-123
   def chunk_file_directory
-    File.join('tmp', 'flow', params[:flowIdentifier])
+    File.join('tmp', 'flow', chunks_params[:flowIdentifier])
   end
 
   ##
   # /tmp/flow/upload.txt
   def final_file_path
-    File.join(final_file_directory, params[:flowFilename])
+    File.join(final_file_directory, chunks_params[:flowFilename])
   end
 
   ##