Fix: Random errors in IE11 due to document.activeElement being an object (#29)

Author: priyajeet

src/components/base.scss

@@ -12,7 +12,6 @@
     height: 100%;
     letter-spacing: .13px;
     margin: 0;
-    min-width: 350px;
     outline: none;
     overflow: hidden;
     padding: 0;

src/util/dom.js

@@ -14,7 +14,7 @@ import { CLASS_CHECKBOX_SPAN, CLASS_BUTTON_CONTENT_SPAN } from '../constants';
  * @return {boolean} true if its one of the above elements
  */
 export function isInputElement(element: HTMLElement | null): boolean {
-    if (!element) {
+    if (!element || !(element instanceof HTMLElement)) {
         return false;
     }
     const tag = element.tagName.toLowerCase();
@@ -29,7 +29,7 @@ export function isInputElement(element: HTMLElement | null): boolean {
  * @return {boolean} true if its one of the above elements
  */
 export function isFocusableElement(element: HTMLElement | null): boolean {
-    if (!element) {
+    if (!element || !(element instanceof HTMLElement)) {
         return false;
     }
     const tag = element.tagName.toLowerCase();