Hang when clicking Math button (OpenLogger)

[af3556]

WFL 1.4.10 with an OpenLogger MZ 0.1807.0; Chrome 73.0.3683.103 (Official Build) (64-bit); macOS 10.14.4 (18E226)

Clicking the Math button causes the UI to hang. Console log extract below.

main.js:28 TypeError: Cannot read property '0' of undefined
    at t.getMetrics (main.js:22)
    at e.detectChangesInternal (main.js:75)
    at e.t.detectChanges (main.js:1)
    at e.t.detectContentChildrenChanges (main.js:1)
    at e.detectChangesInternal (main.js:75)
    at e.t.detectChanges (main.js:1)
    at e.t.detectContentChildrenChanges (main.js:1)
    at e.detectChangesInternal (main.js:75)
    at e.t.detectChanges (main.js:1)
    at e.t.detectViewChildrenChanges (main.js:1)