fix invalid content type leaving upload stuck in preprocessing status (#3896)

app/logical/upload_service/preprocessor.rb

@@ -104,7 +104,7 @@ class UploadService
         upload.status = "preprocessed"
         upload.save!
       rescue Exception => x
-        upload.update(status: "error: #{x.class} - #{x.message}", backtrace: x.backtrace.join("\n"))
+        upload.update(file_ext: nil, status: "error: #{x.class} - #{x.message}", backtrace: x.backtrace.join("\n"))
       end
 
       return upload

test/models/upload_service_test.rb

@@ -489,6 +489,18 @@ class UploadServiceTest < ActiveSupport::TestCase
         end
       end
 
+      context "for an invalid content type" do
+        setup do
+          @source = "http://www.example.com"
+          @service = subject.new(source: @source)
+        end
+
+        should "fail" do
+          upload = @service.start!
+          upload.reload
+          assert_match(/error:/, upload.status)
+        end
+      end
     end
 
     context "#finish!" do