Indentation issue: Args out of range about polymode

[AndreasMatthias]

It seems that syntax-propertize() is trying to look outside the current span. Does the following patch make any sense? It seems to work but I have absolutely no idea what's going on.

--- polymode-methods.el.orig    2015-01-02 23:08:39.611555450 +0100
+++ polymode-methods.el 2015-01-02 23:09:38.615554406 +0100
@@ -534,6 +534,7 @@
       (save-restriction
         (pm--comment-region  1 (nth 1 span))
         (pm/narrow-to-span span)
+        (syntax-ppss-flush-cache 0)
         (funcall pm--indent-line-function-original))
     (pm--uncomment-region 1 (nth 1 span))))