captcha/getdistorts: randomRange requires integers

lib/captcha/getdistorts.js

@@ -13,8 +13,8 @@ module.exports = async (width, height, numDistorts, distortion) => {
 	for (let i = 0; i < randNumDistorts; i++) {
 
 		//start and end of divided width
-		const divStart = (div * i)
-			, divEnd = (div * (i + 1));
+		const divStart = Math.floor(div * i)
+			, divEnd = Math.floor(div * (i + 1));
 
 		//origin coordinate for distortion point
 		const originx = await randomRange(divStart, divEnd)