Madison Beer's new Locket Tour has barely begun, but social media is already flooded with side-by-side comparisons to Sabrina Carpenter's wildly popular 'Short n' Sweet' Tour. After Madison opened the tour in Kraków, Poland, fans quickly began posting clips comparing the stage layouts, pastel merch, retro-glam outfits and theatrical staging. Some accused the singer of copying Sabrina Carpenter's entire era, while others argued both pop stars sim…