[gimp] Bug 738952 - Invalid syntax for (cond) causes a segfault

[Simon Budig <simon src gnome org>]

commit b6946af0e1de3155cfe867e8cca5f927f0fcbe02
Author: Simon Budig <simon budig de>
Date:   Mon May 4 20:03:02 2015 +0200

    Bug 738952 - Invalid syntax for (cond) causes a segfault
    
    Segfault in script-fu, spotted by Pedro Gimeno.

 plug-ins/script-fu/tinyscheme/scheme.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/plug-ins/script-fu/tinyscheme/scheme.c b/plug-ins/script-fu/tinyscheme/scheme.c
index 47c9f3e..06137db 100644
--- a/plug-ins/script-fu/tinyscheme/scheme.c
+++ b/plug-ins/script-fu/tinyscheme/scheme.c
@@ -3144,6 +3144,9 @@ static pointer opexe_1(scheme *sc, enum scheme_opcodes op) {
                if ((sc->code = cdar(sc->code)) == sc->NIL) {
                     s_return(sc,sc->value);
                }
+               if(!sc->code) {
+                    Error_0(sc,"syntax error in cond");
+               }
                if(car(sc->code)==sc->FEED_TO) {
                     if(!is_pair(cdr(sc->code))) {
                          Error_0(sc,"syntax error in cond");