Bug#797363: doesn't occur with current version

[cacatoes at tuxfamily.org]

This bug doesn't occur with currently packaged vcmi versions, buying a 
spell book works fine.
Tested on vcmi 0.99+dfsg+git20190113.f06c8a87-2 (bullseye) and on 
bookworm.
So I think this bug can be closed.

---

As a side note, I wasn't able to load the save game attached to this bug 
report.

Establishing connection...
Found endpoints:
	0:127.0.0.1:3030
Trying connection to 127.0.0.1:3030(0)
Established connection with VCMI 0.99 GITDIR-NOTFOUND (server). UUID: 
6766579e-beca-4b08-a8db-6713f6356198
vcmiserver: /usr/include/boost/optional/optional.hpp:1212: 
boost::optional<T>::reference_type boost::optional<T>::get() [with T = 
boost::filesystem::path; boost::optional<T>::reference_type = 
boost::filesystem::path&]: Assertion `this->is_initialized()' failed.
Aborted
Lost connection to server, ending listening thread!
read: End of file
Error: server failed to close correctly or crashed!
Check /home/fab/.cache/vcmi/server_log.txt for more info

(not exactly more info in server_log.txt)