case T_POINTER:
     params[i].t = T_POINTER;
     origST[i] = ST(i+1);
     if(has_proto) {                                   
-        pointerCallPack(ST(i+1), i, intypes);
-        params[i].p = (char *) SvPV_nolen(ST(i+1));
+        if(SvOK(ST(i+1)) {
+            pointerCallPack(ST(i+1), i, intypes);
+            params[i].p = (char *) SvPV_nolen(ST(i+1));
+        } else {
+            params[i].p = NULL;
+        }
     } else {
         if(SvIOK(ST(i+1)) && SvIV(ST(i+1)) == 0) {
             params[i].p = NULL;
         } else {
             params[i].p = (char *) SvPV_nolen(ST(i+1));
         }
     }

...

         if(params[i].t == T_POINTER && has_proto) {
-            pointerCallUnpack(origST[i], i, intypes);
+            if(SvOK(origST[i]) {
+                pointerCallUnpack(origST[i], i, intypes);
+            }
         }