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: lvm.h,v 2.5.1.1 2007/12/27 13:02:25 roberto Exp $
** Lua virtual machine
** See Copyright Notice in lua.h
*/
#ifndef lvm_h
#define lvm_h
#include "ldo.h"
#include "lobject.h"
#include "ltm.h"
#define tostring(L,o) ((ttype(o) == LUA_TSTRING) || (luaV_tostring(L, o)))
#define tonumber(o,n) (ttype(o) == LUA_TNUMBER || \
(((o) = luaV_tonumber(o,n)) != NULL))
#define equalobj(L,o1,o2) \
(ttype(o1) == ttype(o2) && luaV_equalval(L, o1, o2))
LUAI_FUNC int luaV_lessthan (lua_State *L, const TValue *l, const TValue *r);
LUAI_FUNC int luaV_equalval (lua_State *L, const TValue *t1, const TValue *t2);
LUAI_FUNC const TValue *luaV_tonumber (const TValue *obj, TValue *n);
LUAI_FUNC int luaV_tostring (lua_State *L, StkId obj);
LUAI_FUNC void luaV_gettable (lua_State *L, const TValue *t, TValue *key,
StkId val);
LUAI_FUNC void luaV_settable (lua_State *L, const TValue *t, TValue *key,
StkId val);
LUAI_FUNC void luaV_execute (lua_State *L, int nexeccalls);
LUAI_FUNC void luaV_concat (lua_State *L, int total, int last);
#endif