py: Fix dummy definition of BEGIN/END_ATOMIC_SECTION.
diff --git a/py/objexcept.c b/py/objexcept.c
index 9b22acd..a9c0436 100644
--- a/py/objexcept.c
+++ b/py/objexcept.c
@@ -88,10 +88,10 @@
 
     // Update the 2 variables atomically so that an interrupt can't occur
     // between the assignments.
-    mp_uint_t irq_state = MICROPY_BEGIN_ATOMIC_SECTION();
+    mp_uint_t atomic_state = MICROPY_BEGIN_ATOMIC_SECTION();
     mp_emergency_exception_buf_size = size;
     mp_emergency_exception_buf = buf;
-    MICROPY_END_ATOMIC_SECTION(irq_state);
+    MICROPY_END_ATOMIC_SECTION(atomic_state);
 
     if (old_buf != NULL) {
         m_free(old_buf, old_size);