Experimental null check for CustomBlock.  Shouldn't need this, something outside of spoutplugin is modifying the custom blocks actual ID number, causing this error: https://spoutdev.atlassian.net/browse/LEGACY-608

Signed-off-by: Mike Howe <dockter@almuramc.com>
Merge branch 'master' of https://github.com/Legacy/Spoutcraft