Adding a char at beginning of "WordPress address URL" (siteurl) "destroys" blog

[piuzito]

WP installed in a subdomain

1. In Admin go to "Settings > General"
2. Add for example "a" to the beginning of the "WordPress address (URL)" (siteurl)
3. Click "Save Settings"
4. It gives the following errors:

Warning: strpos() [function.strpos]: Empty delimiter in /home/USER/public_html/blog/wp-admin/includes/file.php on line 76

Warning: strpos() [function.strpos]: Empty delimiter in /home/USER/public_html/blog/wp-admin/includes/file.php on line 76

Warning: Cannot modify header information - headers already sent by (output started at /home/USER/public_html/blog/wp-admin/includes/file.php:76) in /home/USER/public_html/blog/wp-includes/pluggable.php on line 890

Then if going back and click for example again on "Settings > General" it gives a screen with this error:

"One or more database tables are unavailable. The database may need to be repaired."

...

Checking the database the "siteurl" (in wp_options table) was blank (empty) - adding the URL to the "siteurl" (directly in DB) solved the problem.

[SergeyBiryukov]

What is the expected behaviour in this case?

[nacin]

See #10970.