fix case where max feedrates are all 0

src/kiri/mode/cam/export.js

@@ -268,7 +268,7 @@ export function cam_export(print, online) {
             arc = out.emit == 2 || out.emit == 3,
             center = out.center,
             nl = (compact_output && lastGn === gn) ? [] : [gn],
-            maxf = dz < 0 ? maxZd : maxXYd,
+            maxf = (dz < 0 ? maxZd : maxXYd) || speed,
             feed = Math.min(speed || maxf, maxf),
             dist = Math.sqrt(dx * dx + dy * dy + dz * dz),
             newFeed = feed && feed !== pos.f;