Commands may throw exceptions when outside a game

[rolandwalker]

Example

(goto-char (point-max))

M-x pygn-mode-echo-fen-at-pos
; Wrong type argument: integer-or-marker-p, nil

Tree-sitter brought a deeper understanding of the structure of the file, and is naturally more strict. But this does not match the previous behavior. In addition, if an exception is to be thrown, it must be meaningful. This needs testing, and thinking through.

Intuitively, I think some of the defuns could reman strict in their understanding of placement in the buffer, but the commands made more lenient.