Converting from .WAV (PCM) to .MP4 with -acodec copy produces unplayable output

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% ffmpeg -i somewav.wav -acodec copy output.mp4
ffmpeg version 4.0-tessus Copyright (c) 2000-2018 the FFmpeg developers
  built with Apple LLVM version 9.1.0 (clang-902.0.39.1)
(...)

The produced file cannot be decoded by FFmpeg:

% ffmpeg -i output.mp4 decoded.wav
(...)
Decoder (codec none) not found for input stream #0:0

Additionally, nonsensical info appears to be written to MP4 headers regarding the channel count in the stream, the MP4 file sourced from a mono WAV has this:

Stream #0:0(und): Audio: none ([1][0][0][0] / 0x0001), 11025 Hz, stereo (default)

Yet the data within it is most definitely mono.

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Example MP4 file

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Source file that the provided example MP4 was converted from

[Gyan]

FFmpeg does not mux PCM into MP4; MOV works.

The bug here is that ffmpeg doesn't abort with a warning like it does when the audio is being transcoded to PCM and muxed into MP4.

[Carl Eugen Hoyos]

I believe this is a duplicate of ticket #6897.

For future tickets: Please test current FFmpeg git head, nothing else is supported here, and please provide the command line that allows to reproduce the issue together with the complete, uncut console output.