BUILD: server: check->desc always exists

BUILD: server: check->desc always exists

Clang reports this warning :

  src/server.c:872:14: warning: address of array 'check->desc' will
  always evaluate to 'true' [-Wpointer-bool-conversion]

Indeed, check->desc used to be a pointer to a dynamically allocated area
a long time ago and is now an array. Let's remove the useless test.