fix(android): add missing null check for fileTypes (#1368 by @bengy)

android/src/main/java/com/reactnativecommunity/webview/RNCWebViewModule.java

       // convert file extensions to mime types
       if (t.matches("\\.\\w+")) {
         String mimeType = getMimeTypeFromExtension(t.replace(".", ""));
-        mimeTypes[i] = mimeType;
+        if(mimeType != null) {
+          mimeTypes[i] = mimeType;
+        } else {
+          mimeTypes[i] = t;
+        }
       } else {
         mimeTypes[i] = t;
       }
     // when our array returned from getAcceptTypes() has no values set from the webview
     // i.e. <input type="file" />, without any "accept" attr
     // will be an array with one empty string element, afaik
-    return arr.length == 0 || (arr.length == 1 && arr[0].length() == 0);
+    return arr.length == 0 || (arr.length == 1 && arr[0] != null && arr[0].length() == 0);
   }
 
   private PermissionAwareActivity getPermissionAwareActivity() {