Merge pull request #7369 from Gnurou/arrowhelperfix

ArrowHelper: fix undefined reference when using zero-length tails

src/extras/helpers/ArrowHelper.js

@@ -35,11 +35,9 @@ THREE.ArrowHelper = ( function () {
 
 		this.position.copy( origin );
 		
-		if ( headLength < length ) {
-			this.line = new THREE.Line( lineGeometry, new THREE.LineBasicMaterial( { color: color } ) );
-			this.line.matrixAutoUpdate = false;
-			this.add( this.line );
-		}
+		this.line = new THREE.Line( lineGeometry, new THREE.LineBasicMaterial( { color: color } ) );
+		this.line.matrixAutoUpdate = false;
+		this.add( this.line );
 
 		this.cone = new THREE.Mesh( coneGeometry, new THREE.MeshBasicMaterial( { color: color } ) );
 		this.cone.matrixAutoUpdate = false;
@@ -91,10 +89,8 @@ THREE.ArrowHelper.prototype.setLength = function ( length, headLength, headWidth
 	if ( headLength === undefined ) headLength = 0.2 * length;
 	if ( headWidth === undefined ) headWidth = 0.2 * headLength;
 
-	if ( headLength < length ){
-		this.line.scale.set( 1, length - headLength, 1 );
-		this.line.updateMatrix();
-	}
+	this.line.scale.set( 1, Math.max( 0, length - headLength ), 1 );
+	this.line.updateMatrix();
 
 	this.cone.scale.set( headWidth, headLength, headWidth );
 	this.cone.position.y = length;
@@ -104,7 +100,7 @@ THREE.ArrowHelper.prototype.setLength = function ( length, headLength, headWidth
 
 THREE.ArrowHelper.prototype.setColor = function ( color ) {
 
-	if ( this.line !== undefined ) this.line.material.color.set( color );
+	this.line.material.color.set( color );
 	this.cone.material.color.set( color );
 
 };