check the status of the matrix_invert function
check the status of the matrix_invert function

Contrary to the other functions of the matrix module, this one can
fail.
Thanks to Pierre-Marie Pédrot for reporting this.

ShamoX/cairo-ocaml,ShamoX/cairo-ocaml,ShamoX/cairo-ocaml,freedesktop-unofficial-mirror/cairo-ocaml,freedesktop-unofficial-mirror/cairo-ocaml