lua_demux: return nil when read/peek fails.

modules/lua/demux.c

@@ -60,8 +60,12 @@ static int vlclua_demux_peek( lua_State *L )
     demux_t *p_demux = (demux_t *)vlclua_get_this( L );
     int n = luaL_checkint( L, 1 );
     const uint8_t *p_peek;
+
     int i_peek = stream_Peek( p_demux->s, &p_peek, n );
+    if( i_peek > 0 )
         lua_pushlstring( L, (const char *)p_peek, i_peek );
+    else
+        lua_pushnil( L );
     return 1;
 }
 
@@ -71,9 +75,16 @@ static int vlclua_demux_read( lua_State *L )
     const uint8_t *p_read;
     int n = luaL_checkint( L, 1 );
     int i_read = stream_Peek( p_demux->s, &p_read, n );
+
+    if( i_read > 0 )
+    {
         lua_pushlstring( L, (const char *)p_read, i_read );
         int i_seek = stream_Read( p_demux->s, NULL, i_read );
-    assert(i_read==i_seek);
+        assert( i_read == i_seek );
+    }
+    else
+        lua_pushnil( L );
+
     return 1;
 }