Activists on Wednesday briefly pasted a photo of a bloodied mother and child in Gaza over a Picasso painting at a London gallery, calling for an arms embargo on Israel. The National Gallery said two people had been arrested by police after an incident involving Picasso’s 1901 work “Motherhood” and that no damage had been carried out. The Youth Demand group said two protesters stuck a photograph of the mother and child on the protective glass cover over Picasso’s work. A social media video posted by the group showed a security guard taking down the photo. One protester shouted “Free, free Pales…