We are seeing the same error posted by Bas Hendrix in September.  We too would love to implement this, but 

Unexpected runtime error

The runtime has encountered an unexpected error.

Error source

Page Name:/uploadFiles.xsp
Control Id: cf_EmbedUploadedFilesToDoc

Exception

Error while executing JavaScript computed expression
Script interpreter error, line=37, col=43: [TypeError] Exception occurred calling method NotesXspDocument.save() null

JavaScript code

   1: var map = facesContext.getExternalContext().getRequestParameterMap(); 
   2: var fileUploadResponse = map.get('$$xspsubmitvalue'); 
   3: var bSaveDocument = false
   4: 
   5: var fileRichTextItem:String = compositeData.richtTextFieldName
   6: var uploadField:NotesRichTextItem = null;
   7: 
   8: var hdnAllowSubmit:com.ibm.xsp.component.xp.XspInputHidden = getComponent("hdnAllowSubmit");
   9: 
  10: // only upload anything then there is something to upload.
  11: if (hdnAllowSubmit.getValue() == 0){
  12:    if (@Contains(fileUploadResponse, "#UPLOADEDFILE#")){
  13:       var arrFiles:Array = @Explode(fileUploadResponse, ",");
  14: 
  15:       
  16:       if (compositeData.documentDataSource.getDocument().hasItem(fileRichTextItem)){
  17:          uploadField = compositeData.documentDataSource.getDocument().getFirstItem(fileRichTextItem);
  18:          if (uploadField == null){
  19:             uploadField = compositeData.documentDataSource.getDocument().createRichTextItem(fileRichTextItem);
  20:          }
  21:       }else{
  22:          uploadField = compositeData.documentDataSource.getDocument().createRichTextItem(fileRichTextItem);
  23:       }
  24:       
  25: 
  26:       for(i=0;i<@Elements(arrFiles);i=i+1){
  27:          var fileUploadRenamed = new java.io.File(@Word(arrFiles[i], "#UPLOADEDFILE#", 1))
  28:          if (fileUploadRenamed.exists()){
  29:             bSaveDocument = true
  30:             uploadField.embedObject(lotus.domino.local.EmbeddedObject.EMBED_ATTACHMENT, "", fileUploadRenamed.getAbsolutePath(), null);
  31: 
  32:             // rename the file back to its original
  33:             fileUploadRenamed.renameTo(new java.io.File(@Word(arrFiles[i], "#UPLOADEDFILE#", 2)));
  34:          }
  35:       }
  36:       if (bSaveDocument == true){
  37:          compositeData.documentDataSource.save()
  38:          // do not allow to run again
  39:          hdnAllowSubmit.setValue(1);
  40:       }
  41:    }
  42: }

► Stack Trace