Hey, we can’t ‘Sia’

SIA’s “performance art shtick” didn’t work for some fans at her soldout Barclays Center show on Tuesday. The singer (above) hid her face behind her signature two-tone wig at the back of the stage as a 14-year-old girl danced. “Who wants to pay $200 to sit in a crowd and watch a kid while [the singer] is hiding?” wondered one witness. “It could’ve been anyone singing.” Like Trump supporters, “people were yelling, ‘It’s rigged!’ ” Others appreciated the artistry. The Post raved in its review that Sia is “the envy of other pop stars.”