src/vs/workbench/contrib/terminal/browser/terminalGroupService.ts/TerminalGroupService/activeGroup
class TerminalGroupService:	set activeGroup(value: ITerminalGroup | undefined) {
		if (value === undefined) {
			// Setting to undefined is not possible, this can only be done when removing the last group
			return;
		}
		const index = this.groups.findIndex(e => e === value);
		this.setActiveGroupByIndex(index);
	}