Log: fix logging the right IP address when install behind a reverse proxy

src/Log.php

@@ -161,7 +161,7 @@ class Log {
     if (self :: $levels[$level] < self :: $levels[self :: $level]) return true;
     if(self :: $filepath && is_null(self :: $file_fd)) {
       self :: $file_fd = fopen(self :: $filepath, 'a');
-      if (self :: $file_fd === false)
+      if (self :: $file_fd)
         self :: error('Fail to open log file (%s)', self :: $filepath);
     }