Fixes this valgrind finding

==16977== Warning: invalid file descriptor -1 in syscall close()
==16977== Conditional jump or move depends on uninitialised value(s)
==16977==    at 0x544B6B: XkbSendNewKeyboardNotify (xkbEvents.c:62)
==16977==    by 0x540481: ProcXkbGetKbdByName (xkb.c:5330)
==16977==    by 0x4341C5: Dispatch (NXdispatch.c:482)
==16977==    by 0x40EB02: main (main.c:353)
==16977==  Uninitialised value was created by a heap allocation
==16977==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==16977==    by 0x431BD7: NextAvailableClient (dispatch.c:3719)
==16977==    by 0x47B297: AllocNewConnection (connection.c:821)
==16977==    by 0x47B297: EstablishNewConnections (connection.c:910)
==16977==    by 0x463DFE: ProcessWorkQueue (dixutils.c:541)
==16977==    by 0x47635E: WaitForSomething (WaitFor.c:213)
==16977==    by 0x434089: Dispatch (NXdispatch.c:360)
==16977==    by 0x40EB02: main (main.c:353)