Avoid dividing by 0 in erasure interval computation

src/erasure.js

@@ -63,16 +63,20 @@ function cap1(x) {
 }
 
 function erasureInterval(lineStart, lineEnd, erasureCenter, erasureRadius) {
+  const lineLength = distance(lineStart, lineEnd)
+  const distToLine = distanceToLine(lineStart, lineEnd, erasureCenter)
+  if (lineLength === 0) {
+    return distToLine <= erasureRadius ? [0, 1] : [0, 0]
+  }
+
   const projectionPoint = interpolate(
     lineStart,
     lineEnd,
     project(lineStart, lineEnd, erasureCenter),
   )
-  const d = distanceToLine(lineStart, lineEnd, erasureCenter)
-  const halfLength = Math.sqrt(erasureRadius ** 2 - d ** 2)
-  const lineLength = distance(lineStart, lineEnd)
-
   const touchFromStartDist = distance(lineStart, projectionPoint)
+  const halfLength = Math.sqrt(erasureRadius ** 2 - distToLine ** 2)
+
   const touchBeginFromStarDist = touchFromStartDist - halfLength
   const touchEndFromStarDist = touchFromStartDist + halfLength