fix bug in pl_matrix_input test
fix bug in pl_matrix_input test

mwest1066/PrairieLearn,parasgithub/PrairieLearn,parasgithub/PrairieLearn,tbretl/PrairieLearn,mwest1066/PrairieLearn,rbessick5/PrairieLearn,parasgithub/PrairieLearn,mwest1066/PrairieLearn,tbretl/PrairieLearn,rbessick5/PrairieLearn,jakebailey/PrairieLearn,mwest1066/PrairieLearn,rbessick5/PrairieLearn,tbretl/PrairieLearn,jakebailey/PrairieLearn,jakebailey/PrairieLearn,mwest1066/PrairieLearn,parasgithub/PrairieLearn,rbessick5/PrairieLearn,parasgithub/PrairieLearn,tbretl/PrairieLearn,jakebailey/PrairieLearn,tbretl/PrairieLearn,rbessick5/PrairieLearn