1. Use the attach file "test.zul"
2. click insert picture button
3. drag picture left or top will cause NPE

It cause by client sending null value to server
data_1:

{"sheetId":"z3_sheet_8","wgtType":"image","action":"move","wgtId":"z3_pic_0","dx1":null,"dy1":26,"dx2":null,"dy2":13,"col1":null,"row1":0,"col2":null,"row2":4}