QT for some reason messes with XCompose causing broken input (Qt 5 only - Qt 4 did not break anything). In Qt 5.2 and 5.3 this was causing an invalid conversion in chat messages containing these resulting in the bad bytes being stripped. In Qt 5.9 it is still broken, but you at least get a string with something in it. This checks for non-zero converted strings for room creation and chat lines.
/*
** $Id: lmem.h,v 1.31.1.1 2007/12/27 13:02:25 roberto Exp $
** Interface to Memory Manager
** See Copyright Notice in lua.h
*/
#ifndef lmem_h
#define lmem_h
#include <stddef.h>
#include "llimits.h"
#include "lua.h"
#define MEMERRMSG "not enough memory"
#define luaM_reallocv(L,b,on,n,e) \
((cast(size_t, (n)+1) <= MAX_SIZET/(e)) ? /* +1 to avoid warnings */ \
luaM_realloc_(L, (b), (on)*(e), (n)*(e)) : \
luaM_toobig(L))
#define luaM_freemem(L, b, s) luaM_realloc_(L, (b), (s), 0)
#define luaM_free(L, b) luaM_realloc_(L, (b), sizeof(*(b)), 0)
#define luaM_freearray(L, b, n, t) luaM_reallocv(L, (b), n, 0, sizeof(t))
#define luaM_malloc(L,t) luaM_realloc_(L, NULL, 0, (t))
#define luaM_new(L,t) cast(t *, luaM_malloc(L, sizeof(t)))
#define luaM_newvector(L,n,t) \
cast(t *, luaM_reallocv(L, NULL, 0, n, sizeof(t)))
#define luaM_growvector(L,v,nelems,size,t,limit,e) \
if ((nelems)+1 > (size)) \
((v)=cast(t *, luaM_growaux_(L,v,&(size),sizeof(t),limit,e)))
#define luaM_reallocvector(L, v,oldn,n,t) \
((v)=cast(t *, luaM_reallocv(L, v, oldn, n, sizeof(t))))
LUAI_FUNC void *luaM_realloc_ (lua_State *L, void *block, size_t oldsize,
size_t size);
LUAI_FUNC void *luaM_toobig (lua_State *L);
LUAI_FUNC void *luaM_growaux_ (lua_State *L, void *block, int *size,
size_t size_elem, int limit,
const char *errormsg);
#endif