--- alexandria-book-collection-manager-0.7.6/lib/alexandria/ui/new_book_dialog.rb.nothread	2020-11-03 00:29:34.194485720 +0900
+++ alexandria-book-collection-manager-0.7.6/lib/alexandria/ui/new_book_dialog.rb	2020-11-03 00:34:01.426386821 +0900
@@ -281,15 +281,17 @@ module Alexandria
                          get_images_async
                          false # continue == false if you get to here. Stop timeout.
                        end
-                     else
+                     elsif @find_thread
                        # Stop if the book find thread has stopped.
                        @find_thread.alive?
+                     else
+                       true
                      end
           # continue == false if @find_error OR if results are returned
           # timeout ends if continue is false!
 
           # @find_thread.alive? happens after find_thread is done
-          unless continue || @find_thread.alive? || @destroyed
+          unless continue || (@find_thread && @find_thread.alive?) || @destroyed
             notify_end_add_by_isbn
             @button_add.sensitive = false
           end