MonteCarloFill not work properly in demo

When I select "MonteCarloFill" on the interactive showcase page then I have following message in console of the browser:

MonteCarloFill.mjs:173 Uncaught ReferenceError: maxJ is not defined
    at MonteCarloFill.mjs:173:13
    at Array.forEach (<anonymous>)
    at MonteCarloFill.mjs:171:11
    at Array.map (<anonymous>)
    at AcetateMonteCarlo.sprinkle (MonteCarloFill.mjs:117:5)
    at AcetateMonteCarlo.reproject (MonteCarloFill.mjs:227:9)
    at Allocator.forEachBlock (Allocator.mjs:215:5)
    at WrappedSequentialSparseIndices.forEachBlock (SequentialSparseIndices.mjs:51:23)
    at AcetateMonteCarlo.reprojectAll (Dot.mjs:162:17)
    at AcetateMonteCarlo.redraw (Acetate.mjs:608:9)

The map in this case is not displayed, of course.

Opera 85.0.4341.75 Windows 10 64-bit