Fix atomic level

include/spdlog/common.h

@@ -172,7 +172,7 @@ enum class log_level
     n_levels
 };
 
-#if not defined(SPDLOG_NO_ATOMIC_LEVELS)
+#if defined(SPDLOG_NO_ATOMIC_LEVELS)
     using level_t = details::null_atomic_log_level;
 #else
     using level_t = std::atomic<log_level>;

include/spdlog/details/null_mutex.h

@@ -6,7 +6,7 @@
 #include <atomic>
 #include <utility>
 
-// null, no cost dummy "mutex" and dummy "atomic" int
+// null, no cost dummy "mutex" and dummy "atomic" log level
 
 namespace spdlog {
 enum class log_level; // forward declaration
@@ -21,7 +21,6 @@ struct null_mutex
 struct null_atomic_log_level
 {
     spdlog::log_level value;
-    null_atomic_log_level() = default;
 
     explicit null_atomic_log_level(spdlog::log_level new_value)
         : value(new_value)