Use `document` when `getRootNode` is unsupported (#6641)

diff --git a/src/platforms/platform.dom.js b/src/platforms/platform.dom.js
index 03f8486be43777af88d336b0577cc17e417203ab..457cc7c90f89d9b11c74ac89a74f84d716366c15 100644 (file)
--- a/src/platforms/platform.dom.js
+++ b/src/platforms/platform.dom.js
@@ -339,7 +339,7 @@ module.exports = {
                        // If the canvas is in a shadow DOM, then the styles must also be inserted
                        // into the same shadow DOM.
                        // https://github.com/chartjs/Chart.js/issues/5763
-                       var root = canvas.getRootNode();
+                       var root = canvas.getRootNode ? canvas.getRootNode() : document;
                        var targetNode = root.host ? root : document.head;
                        injectCSS(targetNode, stylesheet);
                }