I got Fatal error: Call to a member function initialLanguage() on a non-object in ezcontentobject.php line 1274.
when I tried to install huge package.

Steps to reproduce

It is hard t reproduce for me. But lets to see in the code/
Simplified backtrace:

1. eZPackage::install()
2. eZPackage::installItem() from eZPackage::install() line 1883
3. eZContentObjectPackageHandler::install() from eZPackage::installItem() line 1858
4. eZContentObjectPackageHandler::installContentObjects() from eZContentObjectPackageHandler::install() line 994
5. eZContentObject::unserialize() from eZContentObjectPackageHandler::installContentObjects() line 1056

In this function line 5061

$contentObject = eZContentObject::fetchByRemoteID( $remoteID ); 

And if contentObject (that we are trying to install) exists

if ( !$contentObject )
{
    // does not metter
}
else
{
     $firstVersion = false; //Important!!!!!!!!!!!!
     $description = "Object '$name' already exists.";

      // include_once( 'kernel/classes/ezpackagehandler.php' );
      $choosenAction = eZPackageHandler::errorChoosenAction( self::PACKAGE_ERROR_EXISTS,
                                                                   $options, $description, $handlerType, false );

       switch( $choosenAction )
       {
           case eZPackage::NON_INTERACTIVE:
           case self::PACKAGE_UPDATE:
           {
               // Keep existing contentobject.
           } break;
...

If eZPackage::NON_INTERACTIVE is true
Existing content object should be kept!

After that versions should be unserialized as well:
6. eZContentObjectVersion::unserialize() from eZContentObject::unserialize() line 5172
To this function $firstVersion as FALSE is passed.
7. eZContentObject::createNewVersionIn() from eZContentObjectVersion::unserialize() line 1254
and after that eZContentObject::createNewVersion()

if ( $copyFromVersion == false )
{
    $version = $this->currentVersion();
}

$copyFromVersion is false. So current version of this content object should be fetched.
BUT this object is recently created from package and NO versions exist yet.

Current version cannot be fetched due to it does not exist in new DB.

To prevent this fatal error in

    $initialLanguage = $version->initialLanguage();

eZPackage::NON_INTERACTIVE should be FALSE