Error reading from database in function get_strings of HotPot

When reviewing attempts on mod/hotpot/review.php?id=...

Debug info: ERROR: invalid input syntax for integer: "35,36"
SELECT id,string FROM mdl_hotpot_strings WHERE id = $1
[array (
0 => '35,36',
)]
Stack trace:
line 394 of /lib/dml/moodle_database.php: dml_read_exception thrown
line 232 of /lib/dml/pgsql_native_moodle_database.php: call to moodle_database->query_end()
line 678 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->query_end()
line 1129 of /lib/dml/moodle_database.php: call to pgsql_native_moodle_database->get_records_sql()
line 837 of /mod/hotpot/locallib.php: call to moodle_database->get_records_select()
line 257 of /mod/hotpot/attempt/review.php: call to hotpot::get_strings()
line ? of unknownfile: call to mod_hotpot_attempt_review::review()
line 79 of /mod/hotpot/review.php: call to call_user_func()

It occurs because in hotpot_responses table has a comma sepparated value in the column correct.