codal_port/modaudio: Ensure AudioFrame size is non-zero.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

src/codal_port/modaudio.c

@@ -519,6 +519,11 @@ MP_DEFINE_CONST_OBJ_TYPE(
     );
 
 microbit_audio_frame_obj_t *microbit_audio_frame_make_new(size_t size, uint32_t rate) {
+    // Make sure size is non-zero.
+    if (size == 0) {
+        size = 1;
+    }
+
     microbit_audio_frame_obj_t *res = m_new_obj_var(microbit_audio_frame_obj_t, data, uint8_t, size);
     res->base.type = &microbit_audio_frame_type;
     res->alloc_size = size;