Magento 1.9 – How to Get Current_[entity] from Registry

Let us look what happend here. If you make a look on the line that is expressed by the error, you can see this code

protected function _prepareLayout()
{
    $this->setChild( 'grid',
        $this->getLayout()->createBlock( $this->_blockGroup.'/' . $this->_controller . '_grid',
        $this->_controller . '.grid')->setSaveParametersInSession(true) );
    return parent::_prepareLayout();
}

As you can see, setSaveParametersInSession() function is used inside _prepareLayout() method. This method will invoke by magento, when it starts to prepare layout to render. Here you can see that admin grid container (ie Mage_Adminhtml_Block_Widget_Grid_Container class) is trying to set a child block. If you make a good look there, you can see that, it uses some properties that we are set through custom grid container(ie Afycon_Customercredits_Block_Adminhtml_Credits class) in order to generate the child block. In custom grid container, we are setting these two properties

$this->_controller = 'customercredits_credits';
$this->_blockGroup = 'customercredits';

Using these values, magento first try to generate a block and then set that block as child to grid container. But what happens here is, Magento can't generate a valid block instance due to wrong property values. According to the given value, Magento now trying to create a block customercredits/customercredits_credits_grid( this stands for Afycon_Customercredits_Block_CustomerCredits_Credits_Grid) and it cannot find that block instance defined anywhere. So in effect, Magento cannot set grid block and as a result it throws an error.

So here your grid block is Afycon_Customercredits_Block_Adminhtml_Credits_Grid. In order to autogenerate this class, you need to set

$this->_controller = 'adminhtml_credits';

BIG NOTE

"$this->_blockGroup should hold block alias name that you set through config.xml and $this->_controller should hold the path to your grid container".

Hope that helps

Here getBlock('collections.edit.tab.product') returns null and that is why setCollectionsProducts() is not working. From your layout udpate xml file, collections.edit.tab.product block stands for the block class Gdata_Collections_Block_Adminhtml_Collections_Edit_Tab_Product. I can see that you defined that block file correctly.

So checkout the folder path for that file, it should be app/code/<codePool>/Gdata/Collections/Block/Adminhtml/Collections/Edit/Tab/Product.php.

Also make sure, your layout update xml file resides in admin theme section. That means it's location should be at app\design\adminhtml\default\default\layout\gdata_collections.xml

Also look for any log errors for more details.

clear the cache and try again.