Added compatability PHP 8.0 for Db\Table

Author: Anton Shevchuk

src/Db/Table.php

@@ -293,7 +293,7 @@ public static function findWhere(...$where): array
                         $whereAndTerms[] = $self->name . '.' . $keyName . ' IN (' . $keyValue . ')';
                     } elseif (null === $keyValue) {
                         $whereAndTerms[] = $self->name . '.' . $keyName . ' IS NULL';
-                    } elseif (is_string($keyValue) && ('%' === $keyValue{0} || '%' === $keyValue{-1})) {
+                    } elseif (is_string($keyValue) && ('%' === substr($keyValue, 0, 1) || '%' === substr($keyValue, -1, 1))) {
                         $whereAndTerms[] = $self->name . '.' . $keyName . ' LIKE ?';
                         $whereParams[] = $keyValue;
                     } else {