jpegli encoding failed for black png

[anenasa]

Describe the bug
I tried to encode black png generated with imagemagick convert but failed:

$ cjpegli c.png o.jpg 
Read 100x100 image, 260 bytes.
Encoding [YUV d1.000 AQ p2 OPT]
jpegli encoding failed

To Reproduce
Steps to reproduce the behavior:
cjpegli c.png o.jpg
Expected behavior
jpg created by cjpegli

Screenshots
Test image:

*Environment
*

• OS: Linux
• Compiler version: gcc 13
• CPU type: x86_64
• cjxl/djxl version string: cjxl v0.10.2 e148959 [AVX2,SSE4,SSE2]

Additional context
Add any other context about the problem here.

[Traneptora]

Here's an update from a debug build:

leo@gauss ~/Downloads :) $ umbrielpng 328402633-06cf92c9-8117-423c-a2b5-1c84bccd0462.png 
PNG signature found: 328402633-06cf92c9-8117-423c-a2b5-1c84bccd0462.png
Chunk: IHDR, Size: 25, Offset: 8, CRC32: 5899a8f9
Chunk: bKGD, Size: 14, Offset: 33, CRC32: dd8a13a4
Chunk: tIME, Size: 19, Offset: 47, CRC32: 19d61c72
Chunk: IDAT, Size: 32, Offset: 66, CRC32: 2971b9fc
Chunk: tEXt, Size: 49, Offset: 98, CRC32: 7c9d47d1
Chunk: tEXt, Size: 49, Offset: 147, CRC32: 0dc0ff6d
Chunk: tEXt, Size: 52, Offset: 196, CRC32: c78fc682
Chunk: IEND, Size: 12, Offset: 248, CRC32: ae426082
Size: 100x100, Color: 1-bit Grayscale
leo@gauss ~/Downloads :) $ cjpegli -d 1 328402633-06cf92c9-8117-423c-a2b5-1c84bccd0462.png test.jpg
Read 100x100 image, 260 bytes.
Encoding [YUV d1.000 AQ p2 OPT]
./lib/extras/enc/jpegli.cc:72: JXL_FAILURE: Only full bit depth unsigned types are supported.
./lib/extras/enc/jpegli.cc:368: JXL_RETURN_IF_ERROR code=1: VerifyInput(ppf)
jpegli encoding failed

[eustas]

Will take a look. Likely we need to add an option to change bit-ness it this case.