validate props

src/components/Canvas.vue

@@ -28,6 +28,13 @@ const clearCanvas = () => {
 const render = () => {
   const { vMargin, vRotation, hMargin, hMargin2, imageWidth, imageHeight } = props;
 
+  if (vMargin < 1 || hMargin < 1 || hMargin2 < 1) {
+    return
+  }
+  if (imageWidth < 1 || imageHeight < 1) {
+    return
+  }
+
   clearCanvas();
 
   var hMargins = [hMargin, hMargin2];