added missing default mime icon

src/uppy/getFileTypeIcon.js

 // all icons taken from https://material.io/resources/icons
 export default function getIconByMime (fileType) {
   const defaultChoice = {
-    icon: 'any'
+    bgColor: '#5a5e69',
+    iconColor: 'white',
+    icon: 'description'
   }
 
   if (!fileType) return defaultChoice