[psaux] Add safety guard (#54985).

* src/psaux/psobjs.c (cff_builder_close_contour): Do it.

ChangeLog

@@ -1,3 +1,9 @@
+2018-11-09  Young Xiao  <yangx92@hotmail.com>
+
+	[psaux] Add safety guard (#54985).
+
+	* src/psaux/psobjs.c (cff_builder_close_contour): Do it.
+
 2018-11-08  Alexei Podtelezhnikov  <apodtele@gmail.com>
 
 	* builds/unix/configure.raw: Require `windows.h' for windres.

src/psaux/psobjs.c

@@ -2042,6 +2042,14 @@
     first = outline->n_contours <= 1
             ? 0 : outline->contours[outline->n_contours - 2] + 1;
 
+    /* in malformed fonts it can happen that a contour was started */
+    /* but no points were added                                    */
+    if ( outline->n_contours && first == outline->n_points )
+    {
+      outline->n_contours--;
+      return;
+    }
+
     /* We must not include the last point in the path if it */
     /* is located on the first point.                       */
     if ( outline->n_points > 1 )