Fix gdb pretty printer (#4343)

Author: MrJia1997

tools/gdb_pretty_printer/nlohmann-json.py

@@ -17,16 +17,16 @@ def json_lookup_function(val):
     if m := ns_pattern.fullmatch(str(val.type.strip_typedefs().name)):
       name = m.group('name')
       if name and name.startswith('basic_json<') and name.endswith('>'):
-          m = ns_pattern.fullmatch(str(val['m_type']))
+          m = ns_pattern.fullmatch(str(val["m_data"]['m_type']))
           t = m.group('name')
           if t and t.startswith('detail::value_t::'):
               try:
-                  union_val = val['m_value'][t.removeprefix('detail::value_t::')]
+                  union_val = val["m_data"]['m_value'][t.removeprefix('detail::value_t::')]
                   if union_val.type.code == gdb.TYPE_CODE_PTR:
                       return gdb.default_visualizer(union_val.dereference())
                   else:
                       return JsonValuePrinter(union_val)
               except Exception:
-                  return JsonValuePrinter(val['m_type'])
+                  return JsonValuePrinter(val["m_data"]['m_type'])
 
 gdb.pretty_printers.append(json_lookup_function)