Description:
------------
To develop a work around for Bug 59376, where I cannot call ->addField('name', 
false), since false falls back to blank and causes an error to Solr, I've tried to 
extend SolrDocument, but it incurs an error.

Either SolrDocument should be Final or should be extendible without error.


Test script:
---------------
class Model_SolrDocument extends SolrDocument
{
        public function addField($fieldName, $fieldValue)
        {
                if (is_bool($fieldValue))
                        $fieldValue = ($fieldValue ? '1' : '0');
                return parent::addField($fieldName, $fieldValue);
        }
}

$doc = new Model_SolrDocument();
$doc->addField('testname', 'testvalue');



Expected result:
----------------
For the class to be extendible and in this example testname=>testvalue keypair 
added to the SolrDocument; OR for a fatal error saying my class may not inherit 
from final class.


Actual result:
--------------
Warning: SolrDocument::__get(): Invalid Document Index 0. HashTable index does 
not exist. in /path/to/script.php on line 11

Call Stack:
    0.0005     238664   1. {main}() /path/to/script.php:0
    0.0006     239920   2. Model_SolrDocument->addField() /path/to/script.php:18
    0.0006     240008   3. SolrDocument->addField() /path/to/script.php:11

Warning: SolrDocument::__get(): Internal Error 1008 generated from 
/tmp/pear/temp/solr/solr_functions_helpers.c 176 solr_fetch_document_entry. The 
observed error is a possible side-effect of an illegal/unsupported operation in 
userspace. Please check the documentation and try again later. in 
/path/to/script.php on line 11

Call Stack:
    0.0005     238664   1. {main}() /path/to/script.php:0
    0.0006     239920   2. Model_SolrDocument->addField() /path/to/script.php:18
    0.0006     240008   3. SolrDocument->addField() /path/to/script.php:11

Warning: Unknown: Invalid Document Index 0. HashTable index does not exist. in 
Unknown on line 0

Warning: Unknown: Internal Error 1008 generated from 
/tmp/pear/temp/solr/solr_functions_helpers.c 176 solr_fetch_document_entry. The 
observed error is a possible side-effect of an illegal/unsupported operation in 
userspace. Please check the documentation and try again later. in Unknown on 
line 0