dbghelp: In const types, force 'void' type when none is found.

dlls/dbghelp/dwarf.c

@@ -1319,7 +1319,11 @@ static struct symt* dwarf2_parse_volatile_type(dwarf2_parse_context_t* ctx,
 
     TRACE("%s, for %s\n", dwarf2_debug_ctx(ctx), dwarf2_debug_di(di));
 
-    ref_type = dwarf2_lookup_type(ctx, di);
+    if (!(ref_type = dwarf2_lookup_type(ctx, di)))
+    {
+        ref_type = ctx->symt_cache[sc_void];
+        assert(ref_type);
+    }
     if (dwarf2_get_di_children(ctx, di)) FIXME("Unsupported children\n");
     di->symt = ref_type;