Fixed analyzer warnings

src/details/async_log_msg.cpp

@@ -34,6 +34,7 @@ async_log_msg::async_log_msg(async_log_msg &&other) noexcept
 }
 
 async_log_msg &async_log_msg::operator=(const async_log_msg &other) {
+    if (this == &other) return *this;
     log_msg::operator=(other);
     msg_type_ = other.msg_type_;
     buffer_.clear();
@@ -43,6 +44,7 @@ async_log_msg &async_log_msg::operator=(const async_log_msg &other) {
 }
 
 async_log_msg &async_log_msg::operator=(async_log_msg &&other) noexcept {
+    if (this == &other) return *this;
     log_msg::operator=(other);
     msg_type_ = other.msg_type_;
     buffer_ = std::move(other.buffer_);