Reproduction steps:

1) Create a custom game with a custom hero
2) Do not specify talent tree names.
3) Start the custom game. Hover over the talent tree with the mouse.

Expected result:

The talent tree has no names for its talents (empty string).

Actual result:

Dota 2 crashes with a segmentation fault.

Suspected cause:

Null pointer dereference when these variables are left undefined by the map creator. The bug will happen in both Linux and Windows in any live version of dota newer than the patch from 22nd january 2017. If these talent names are required fields, the game mode probably should error out instead of crash the whole program.