y axis can use the wrong min/max

[dericed]

using ffmpeg -f lavfi -i testsrc2 -f lavfi -i sine -t 10 test.mkv again.

Load the file (I'm just using the signalstats filter and no qctools report and only Y, U, and V plots visible). So it looks like this

Then enable the "Differences" graph and it has the top of the graph cut off.

But if I switch from the graph view, to list view, and back to graph view, then the y-axis min and max is okay.

[dericed]

Noting that if I enable the PSNR filter, then even if I toggle from graph/list/graph the y axis still never seems to define so graph stays blank. But some of the values in the PSNR data set are not numeric but 'inf'. So may we need to say that if a plot value = "inf" then plot to top of displayed graph (or bottom for -inf).