Remove unnecessary call to mbedtls_mpi_free() in MPI tests
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 63e0e97..3379a99 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -257,8 +257,6 @@
     TEST_INVALID_PARAM_RET( MBEDTLS_ERR_MPI_BAD_INPUT_DATA,
                             mbedtls_mpi_inv_mod( &X, &X, NULL ) );
 
-    mbedtls_mpi_free( NULL );
-
 exit:
     return;
 }