Problem in grid mode when hiding initial columns

Hi, I've found a couple of problems.

1 - Test case:

Open Product window and select all records
Change to grid mode
Hide the first column (Client)
Navigate to one of the records below, back and forth - changed to edit mode, etc. And in some moment this error started appearing every time I change record:

===========> zkoss.handleError:1130: >>java.lang.NumberFormatException: For input string: ""
>> at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
>> at java.lang.Integer.parseInt(Integer.java:468)
>> at java.lang.Integer.parseInt(Integer.java:497)
>> at org.adempiere.webui.panel.LoginPanel$1.onEvent(LoginPanel.java:205)
>> at org.zkoss.zk.ui.impl.EventProcessor.process0(EventProcessor.java:197)
>> at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:141)
>> at org.zkoss.zk.ui.impl.EventProcessingThreadImpl.process0(EventProcessingThreadImpl.java:519)
>> at org.zkoss.zk.ui.impl.EventProcessingThreadImpl.run(EventProcessingThreadImpl.java:446)
[56]

____________________

2 - Test case:

Did the same test opening Freight Category window (just 2 records so grid mode is a lot faster).

Hide Client
navigated to second row, and then first
Hide Organization
navigated to second row, and then first

This error started to appear on every change of record:

===========> zkoss.handleError:1130: >>java.lang.NullPointerException
>> at org.adempiere.webui.component.GridPanel.focusToRow(GridPanel.java:465)
>> at org.adempiere.webui.component.GridPanel.onPostSelectedRowChanged(GridPanel.java:433)
>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>> at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
>> at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>> at java.lang.reflect.Method.invoke(Method.java:597)
>> at org.zkoss.zk.ui.impl.EventProcessor.process0(EventProcessor.java:209)
>> at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:141)
>> at org.zkoss.zk.ui.impl.EventProcessingThreadImpl.process0(EventProcessingThreadImpl.java:519)
>> at org.zkoss.zk.ui.impl.EventProcessingThreadImpl.run(EventProcessingThreadImpl.java:446)
[56]

Regards,

Carlos Ruiz