Custom Font is not loaded after loading a texture pack

Verification builds:
#339699

Summary:
Loading a texture pack containing new font does not unload and load glyphs directly after returning to start screen (resulting in vanilla font instead of custom font).
Closing and Re-loading game, is loading correctly the custom font.

Impact:
The texture pack looks half-loaded (font is very visible in the case of PureBDcraft)
It could look super weird in case of another texture pack with custom font because then, the previous custom font stays with newly loaded texture pack.

Repro Steps:
0. Be sure to be without any Texture Pack
1. Load texture pack with custom font (PureBDcraft for example)
2. Return to start screen and see that the previous font is not unloaded and new font not loaded

Observed Results:
Texture pack has wrong font loaded

Expected Results:
Texture pack has right font loaded directly after applying texture pack for the first time

Screenshots/Videos attached: No

Notes:
Mentionned in MCM-12