Commented out the code that caused segfault when "plot v(x)" command is issued.

src/frontend/parse.c

@@ -865,10 +865,10 @@ free_pnode(struct pnode *t)
     free_pnode(t->pn_next);
      tfree(t->pn_name); /* va: it is a copy() of original string, can be free'd */
     /* va: tfree struct func, allocated within parser */
-    if (t->pn_func!=NULL) {
-    	tfree(t->pn_func->fu_name); /* va: name is a copy of original string */
-    	tfree(t->pn_func);    	    /* va: t->pn_func->fu_func must not tfree'd */
-    }
+//    if (t->pn_func!=NULL) {
+//    	tfree(t->pn_func->fu_name); /* va: name is a copy of original string */
+//    	tfree(t->pn_func);    	    /* va: t->pn_func->fu_func must not tfree'd */
+//    }
     if (t->pn_value)
         vec_free(t->pn_value); /* patch by Stefan Jones */   
     tfree(t);