well actually it is suppose to happen if you walk into grass with no pokemon the game would crash thats why the game gives you a pokemon to use
ps what are game modes
What I meant was is that you should be unable to go to the grass before getting your starter
Gamemodes are mods for the game
If you go to the game folder(the folder that is in the same folder as the launcher) you will see a folder labeled "GameModes" you can download GameModes and extract them into that folder. Then when you start a new game you can choose to play that version instead of the main version.
Silver's Soul is my GameMode and the download is linked in my signature