BUG #17302: gist index prevents insertion of some data

The following bug has been logged on the website:

Bug reference: 17302
Logged by: Alexander Lakhin
Email address: exclusion(at)gmail(dot)com
PostgreSQL version: 14.1
Operating system: Ubuntu 20.04
Description:

The last statement in the following sequence of queries:
CREATE TABLE point_tbl (f1 point);
CREATE INDEX gpointind ON point_tbl USING gist (f1);
INSERT INTO point_tbl SELECT '(0,0)'::point FROM generate_series(1, 1000)
g;
INSERT INTO point_tbl VALUES ('(1e-300,-1e-300)'::point);
produces:
ERROR: value out of range: underflow
(The error occurs inside gist_box_penalty()->box_penalty()->size_box().)
But the following sequence:
CREATE TABLE point_tbl (f1 point);
INSERT INTO point_tbl SELECT '(0,0)'::point FROM generate_series(1, 1000)
g;
INSERT INTO point_tbl VALUES ('(1e-300,-1e-300)'::point);
executes without an error. Moreover, the same index can be created
successfully after the insertion. The error is also depends on number of the
points inserted in the first step.