SeeAssembler: PHP Notice:  Uninitialized string offset: 0 for $reference

Sometimes `$reference[0]` is not set.

Here is the stacktrace
```
phpdoc -c phpdoc.xml
Collecting files .. OK
Initializing parser .. OK
Parsing files
Parsing [REDACTED]
Parsing [REDACTED]
PHP Notice:  Uninitialized string offset: 0 in /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/Builder/Reflector/Tags/SeeAssembler.php on line 51
PHP Stack trace:
PHP   1. {main}() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/bin/phpdoc:0
PHP   2. phpDocumentor\Application->run() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/bin/phpdoc:41
PHP   3. Symfony\Component\Console\Application->run() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Application.php:186
PHP   4. Symfony\Component\Console\Application->doRun() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/symfony/console/Symfony/Component/Console/Application.php:124
PHP   5. Symfony\Component\Console\Application->doRunCommand() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/symfony/console/Symfony/Component/Console/Application.php:193
PHP   6. Symfony\Component\Console\Command\Command->run() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/symfony/console/Symfony/Component/Console/Application.php:887
PHP   7. phpDocumentor\Command\Project\RunCommand->execute() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/symfony/console/Symfony/Component/Console/Command/Command.php:252
PHP   8. Symfony\Component\Console\Command\Command->run() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Command/Project/RunCommand.php:253
PHP   9. phpDocumentor\Parser\Command\Project\ParseCommand->execute() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/symfony/console/Symfony/Component/Console/Command/Command.php:252
PHP  10. phpDocumentor\Parser\Parser->parse() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Parser/Command/Project/ParseCommand.php:205
PHP  11. phpDocumentor\Parser\Parser->parseFileIntoDescriptor() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Parser/Parser.php:319
PHP  12. phpDocumentor\Parser\File->parse() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Parser/Parser.php:359
PHP  13. phpDocumentor\Descriptor\ProjectDescriptorBuilder->buildFileUsingSourceData() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Parser/File.php:67
PHP  14. phpDocumentor\Descriptor\ProjectDescriptorBuilder->buildDescriptor() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/ProjectDescriptorBuilder.php:99
PHP  15. phpDocumentor\Descriptor\Builder\Reflector\FileAssembler->create() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/ProjectDescriptorBuilder.php:130
PHP  16. phpDocumentor\Descriptor\Builder\Reflector\FileAssembler->addClasses() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/Builder/Reflector/FileAssembler.php:65
PHP  17. phpDocumentor\Descriptor\ProjectDescriptorBuilder->buildDescriptor() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/Builder/Reflector/FileAssembler.php:137
PHP  18. phpDocumentor\Descriptor\Builder\Reflector\ClassAssembler->create() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/ProjectDescriptorBuilder.php:130
PHP  19. phpDocumentor\Descriptor\Builder\Reflector\ClassAssembler->addConstants() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/Builder/Reflector/ClassAssembler.php:58
PHP  20. phpDocumentor\Descriptor\ProjectDescriptorBuilder->buildDescriptor() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/Builder/Reflector/ClassAssembler.php:77
PHP  21. phpDocumentor\Descriptor\Builder\Reflector\ConstantAssembler->create() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/ProjectDescriptorBuilder.php:130
PHP  22. phpDocumentor\Descriptor\Builder\Reflector\AssemblerAbstract->assembleDocBlock() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/Builder/Reflector/ConstantAssembler.php:43
PHP  23. phpDocumentor\Descriptor\ProjectDescriptorBuilder->buildDescriptor() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/Builder/Reflector/AssemblerAbstract.php:40
PHP  24. phpDocumentor\Descriptor\Builder\Reflector\Tags\SeeAssembler->create() /srv/lib/phpDocumentor/phpDocumentor-2/vendor/phpdocumentor/phpdocumentor/src/phpDocumentor/Descriptor/ProjectDescriptorBuilder.php:130
```