I will have a look.

->BM: Please take over. Thanks.

The problem here is that on resize, the model is changed, i.e., the font size is
rescaled according to the visible area size, which may result in a 0 font size
for a 0 visible area. To prevent this a minimum font size of 2pt was already
introduced.
Now there is also a minimum size for the visible area of 200 x 200 (1/100 of a
mm), which is so small that you wouldn't see any meaningful chart, but resizing
maintains the font size -- roughly.  As font size items contain long values,
there are still minor changes, but the behaviour is "better" now.

One additional note: You don't have to be in edit mode to reproduce this bug, it
is only easier to get there, because in edit mode the rectangle will stay zero
size when moving the mouse cursor beyond the upper left corner, whereas in
non-edit mode the lower right corner becomes the new upper left corner in this
case. (Difficult to explain, but you will know what I mean when you try it, I
hope ...)

reopened for resend

please verify in CWS bm4

resetting to fixed

verified in cws bm4

ok in master src680_m74