src/vs/workbench/contrib/terminal/browser/xterm/commandNavigationAddon.ts/CommandNavigationAddon/_registerMarkerOrThrow
class CommandNavigationAddon:	private _registerMarkerOrThrow(xterm: Terminal, cursorYOffset: number): IMarker {
		const marker = xterm.registerMarker(cursorYOffset);
		if (!marker) {
			throw new Error(`Could not create marker for ${cursorYOffset}`);
		}
		return marker;
	}