Fix #1527

include/spdlog/pattern_formatter.h

@@ -80,7 +80,7 @@ public:
     using custom_flags = std::unordered_map<char, std::unique_ptr<custom_flag_formatter>>;
 
     explicit pattern_formatter(std::string pattern, pattern_time_type time_type = pattern_time_type::local,
-        std::string eol = spdlog::details::os::default_eol, custom_flags custom_user_flags = {});
+        std::string eol = spdlog::details::os::default_eol, custom_flags custom_user_flags = {{}});
 
     // use default pattern is not given
     explicit pattern_formatter(pattern_time_type time_type = pattern_time_type::local, std::string eol = spdlog::details::os::default_eol);