create: "property variant img: {'0'} not accepted

I tried to create an item that could be used to hold an array of elements
(strings), dynamically generated. They are to be stored as a property of
a "glossary" object (a Qml Item). I created a separate file called "Img_glossary.qml"
in the same directory as the project.

In the project qml file I invoked the "Img_glossary" object specifying a size
of 10, and prefix and suffix ( custom property values) when I run the debugger
I receive a message:

file:​/​/​/​home/​leemke/​proj/​qt/​Img_​glossary/​Img_​glossary.​qml:​7:​4:​ Unable to assign QJSValue to QString

Yet when I review documentation, I seem to be following the example.
I have included 3 snapshots. Two of them show the 2 qml files, and
the fourth is a snapshot of the documentation.

What is wrong? (documentation or something I did)?