Fix #295: List accessing invalid memory

Author: tavmem

src/kx.c

@@ -790,11 +790,12 @@ Z K ex2(V*v, K k)  //execute words --- all returns must be Ks. v: word list, k:
 
   if(bk(v[1])) {
     K z= ex_(*v,1);
-    if(prnt && kV(prnt)[PARAMS] && !kK(prnt)[PARAMS]->n && kV(z)[LOCALS] && !kK(z)[LOCALS]->n) {
-      kV(z)[CACHE_TREE]=kclone(kK(prnt)[CACHE_TREE]); prnt=z; }
-    else if(prnt && kV(prnt)[LOCALS] && kK(prnt)[LOCALS]->n && kV(z)[PARAMS] && kK(z)[PARAMS]->n) {
-      K j0=dot_monadic(kV(z)[PARAMS]); K j1=dot_monadic(kV(prnt)[CACHE_TREE]); 
-      K j2=join(j0,j1); kV(z)[CACHE_TREE]=dot_monadic(j2); cd(j0); cd(j1); cd(j2); }
+    if(prnt && z->t==7) {
+      if(kV(prnt)[PARAMS] && !kK(prnt)[PARAMS]->n && kV(z)[LOCALS] && !kK(z)[LOCALS]->n) {
+        kV(z)[CACHE_TREE]=kclone(kK(prnt)[CACHE_TREE]); prnt=z; }
+      else if(kV(prnt)[LOCALS] && kK(prnt)[LOCALS]->n && kV(z)[PARAMS] && kK(z)[PARAMS]->n) {
+        K j0=dot_monadic(kV(z)[PARAMS]); K j1=dot_monadic(kV(prnt)[CACHE_TREE]); 
+        K j2=join(j0,j1); kV(z)[CACHE_TREE]=dot_monadic(j2); cd(j0); cd(j1); cd(j2); } }
     R z; }
 
   if(!VA(*v) && (offsetColon == v[1] || (VA(v[1]) && offsetColon==v[2]) ) ) //Handle assignment