added removal of secrets config file if last account is removed

bitwardenBackup.py

@@ -445,7 +445,11 @@ if __name__ == "__main__":
                     if not ask_for_confirmation("Are you sure you wish to delete {} account? ".format(account_to_delete)):
                         break
                     del accounts[account_to_delete]
-                    write_config_file(accounts, secrets_config_file)
+                    if len(accounts) == 0:
+                        # no more accounts, remove secrets file
+                        os.remove(secrets_config_file)
+                    else:
+                        write_config_file(accounts, secrets_config_file)
                     break
 
                 # Quit the config