nir/vars_to_ssa: Handle missing struct members in foreach_deref_node

This can happen if, for instance, you have an array of structs and there
are both direct and wildcard references to the same struct and some
members only have direct or only have indirect.

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Cc: mesa-stable@lists.freedesktop.org

src/compiler/nir/nir_lower_vars_to_ssa.c

@@ -245,8 +245,12 @@ foreach_deref_node_worker(struct deref_node *node, nir_deref *deref,
 
       case nir_deref_type_struct: {
          nir_deref_struct *str = nir_deref_as_struct(deref->child);
-         return foreach_deref_node_worker(node->children[str->index],
-                                          deref->child, cb, state);
+         if (node->children[str->index] &&
+             !foreach_deref_node_worker(node->children[str->index],
+                                        deref->child, cb, state))
+            return false;
+
+         return true;
       }
 
       default: