BUG/MINOR: hlua: Don't forget the return statement after a hlua_yieldk()

In hlua_applet_tcp_getline_yield(), the function may yield if there is no
data available. However we must take care to add a return statement just
after the call to hlua_yieldk(). I don't know the details of the LUA API,
but at least, this return statement fix a build error about uninitialized
variables that may be used.

It is a 3.3-specific issue. No backport needed.

src/hlua.c

@@ -5312,6 +5312,7 @@ __LJMP static int hlua_applet_tcp_getline_yield(lua_State *L, int status, lua_KC
 	if (ret == 0) {
 		applet_need_more_data(luactx->appctx);
 		MAY_LJMP(hlua_yieldk(L, 0, 0, hlua_applet_tcp_getline_yield, TICK_ETERNITY, 0));
+		return 0;
 	}
 
 	/* End of data: commit the total strings and return. */