--- a/src/gd_out.c    2011-03-05 11:51:50.000000000 +0100
+++ b/src/gd_out.c   2021-02-23 15:23:00.434133429 +0100
@@ -212,6 +212,6 @@
      *  the right of the last character for the fixed width
      *  font.
      */
-    return rect[2] - 1;
+    return rect[2] ? rect[2] - 1 : 0;
 #endif
 }