platform.isAttached should return false if canvas is false-y (#11707)

* platform.isAttached should return false if canvas is false-y

* change styling to conform to codeclimate linter

Author: DAcodedBEAT

src/helpers/helpers.dom.ts

@@ -142,7 +142,7 @@ function getContainerSize(canvas: HTMLCanvasElement, width: number, height: numb
   let maxWidth: number, maxHeight: number;
 
   if (width === undefined || height === undefined) {
-    const container = _getParentNode(canvas);
+    const container = canvas && _getParentNode(canvas);
     if (!container) {
       width = canvas.clientWidth;
       height = canvas.clientHeight;

src/platform/platform.dom.js

@@ -383,7 +383,7 @@ export default class DomPlatform extends BasePlatform {
 	 * @param {HTMLCanvasElement} canvas
 	 */
   isAttached(canvas) {
-    const container = _getParentNode(canvas);
+    const container = canvas && _getParentNode(canvas);
     return !!(container && container.isConnected);
   }
 }