Call dav1d_data_unref(&codec->internal->dav1dData) in
dav1dCodecDestroyInternal(). This frees codec->internal->dav1dData after
a dav1d_send_data() failure.

Remove the dav1d_data_unref() call in dav1dFeedData(). It is a no-op.
If codec->internal->dav1dData.sz is 0, we don't need to free
codec->internal->dav1dData.

Speeds up the build process and lowers memory requirements while compiling a little.

This makes it easier to analyze the side effects of the code.

…eeding to decode the frame

The following local modification to cJSON.c in libavif commit
a7699ef is in the cJSON upstream:

     /* This checks for NaN and Infinity */
-    if ((d * 0) != 0)
+    if (isnan(d))

In the cJSON upstream, that line reads:

    if (isnan(d) || isinf(d))

decoder->image is set to NULL only in avifDecoderCleanup(), which is
only called in avifDecoderDestroy() and at the beginning of
avifDecoderParse(). Therefore, after decoder->image is allocated in
avifDecoderParse(), decoder->image cannot be NULL.

In avif.h, instead of saying when decoder->image "can be NULL", say when
decoder->image "is invalid".

…array-argument)

Clean up the calculations of UV width and height. If the chroma shift is
1, we need to add 1 to width or height before right shifting by 1. This
can be written in a branch-free form.

Also clean up some code in src/codec_aom.c:
1. The type of the 'flags' parameter of aom_codec_enc_init() is
aom_codec_flags_t.
2. The memset() calls in a for loop can be merged because the row
strides are contiguous.

The following check ensures colorOBUItem is not null:

2033         if (!colorOBUItem) {
2034             return AVIF_RESULT_NO_AV1_ITEMS_FOUND;
2035         }

After this check, colorOBUItem is dereferenced without further checking
in multiple places.

Actually use the outTiming paramter in avifDecoderNthImageTiming(). It
was still using decoder->imageTiming in the copied code.