diff --git a/src/main/java/cit/PureATN/PenUser.java b/src/main/java/cit/PureATN/PenUser.java
index b224208..f857054 100644
--- a/src/main/java/cit/PureATN/PenUser.java
+++ b/src/main/java/cit/PureATN/PenUser.java
@@ -207,6 +207,7 @@
 				}
 			} else {
 				PNode layer = Note.theapp.getCanvas().getLayer();
+				if (squiggle == null) return;
 				if (squiggle.tempPts.size() < 3) {
 					layer.removeChild(squiggle);
 					squiggle = null;