Millwall extended their unbeaten streak to six following a stalemate with play-off chasing Charlton in the south London derby at The Valley.Lee Gregory had the best chance of the first half, but his lobbed effort just crept wide.Charlton, who had top-scorer Josh Magennis and debutant Lewis Page withdraw during the opening exchanges through injury, responded with a volleyed effort from Nathan Byrne which tested the palms of Jordan Archer.After a drab start to the second-half, Millwall were the first to force a chance in the shape of substitute Shane Ferguson, who flashed his volley wide.The Lions then increased the pressure with Steve Morison seeing a goal-bound shot cleared by Jorge Teixeira before Shaun Hutchinson should have done better with a header that went past the post.Centre-back Byron Webster failed to get his header from Shaun Williams' corner on target while Gregory somehow saw a header go just wide.Following the full-time whistle, Teixeira saw red for an off-the-ball incident to conclude a lively south London derby.