Assertion failure in "create a basic audio plug-in" tutorial


I’m on MacOS 11.1 using Juce 6.0.5 and Xcode 12.3
I just downloaded Juce and I’m trying to follow the tutorials.
Trying to run the code from the in the " Create a simple GUI control" section of this page JUCE: Tutorial: Create a basic Audio/MIDI plugin, Part 2: Coding your plug-in yields the following error message :

JUCE Assertion failure in juce_AudioProcessor.cpp:366

The file in question is JUCE Modules/juce_audio_processors/processors/juce_AudioProcessor.cpp

and the line which causes the failure is
jassert (success && newNumIns == getTotalNumInputChannels() && newNumOuts == getTotalNumOutputChannels());

I checked and newNumIns is set to 1 while getTotalNumInputChannels() gives 2.
Where does it come from and how can I fix this?
Seems to me that the internal microphone from the Mac only has one input.