Call to a member function label() on null in Drupal\entity_browser_block\Plugin\Block\EntityBrowserBlock::processTable()

Steps to reproduce

• Create an custom inline block type
• Add some blocks
• Place the block in a layout builder region on a node with entity browser block
• Delete the custom inline block content source
• The entity browser block table will get a null entity and one is left with a broken block

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Error: Call to a member function label() on null in Drupal\entity_browser_block\Plugin\Block\EntityBrowserBlock::processTable() (line 173 of modules/contrib/entity_browser_block/src/Plugin/Block/EntityBrowserBlock.php).
Drupal\entity_browser_block\Plugin\Block\EntityBrowserBlock::processTable(Array, Object, Array)
call_user_func_array(Array, Array) (Line: 1010)

This patch makes the entity browser block usable again.