Cant create page.

When i try save page, i get "Crikey! There was an error."
Here's the copied info.
Whoops\Exception\ErrorException thrown with message "Trying to access array offset on value of type null"

Stacktrace:
```
#43 Whoops\Exception\ErrorException in /home/kociemie/SP/user/plugins/admin/classes/adminbasecontroller.php:736
#42 Grav\Common\Debugger:deprecatedErrorHandler in /home/kociemie/SP/user/plugins/admin/classes/adminbasecontroller.php:736
#41 Grav\Plugin\Admin\AdminBaseController:storeFiles in /home/kociemie/SP/user/plugins/admin/classes/admincontroller.php:722
#40 Grav\Plugin\Admin\AdminController:taskSave in /home/kociemie/SP/user/plugins/admin/classes/adminbasecontroller.php:106
#39 Grav\Plugin\Admin\AdminBaseController:execute in /home/kociemie/SP/user/plugins/admin/admin.php:311
#38 Grav\Plugin\AdminPlugin:initializeController in /home/kociemie/SP/user/plugins/admin/admin.php:371
#37 Grav\Plugin\AdminPlugin:onPagesInitialized in /home/kociemie/SP/vendor/symfony/event-dispatcher/EventDispatcher.php:264
#36 Symfony\Component\EventDispatcher\EventDispatcher:doDispatch in /home/kociemie/SP/vendor/symfony/event-dispatcher/EventDispatcher.php:239
#35 Symfony\Component\EventDispatcher\EventDispatcher:callListeners in /home/kociemie/SP/vendor/symfony/event-dispatcher/EventDispatcher.php:73
#34 Symfony\Component\EventDispatcher\EventDispatcher:dispatch in /home/kociemie/SP/system/src/Grav/Common/Grav.php:592
#33 Grav\Common\Grav:fireEvent in /home/kociemie/SP/system/src/Grav/Common/Processors/PagesProcessor.php:52
#32 Grav\Common\Processors\PagesProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#31 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#30 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/TwigProcessor.php:38
#29 Grav\Common\Processors\TwigProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#28 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#27 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/AssetsProcessor.php:39
#26 Grav\Common\Processors\AssetsProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#25 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#24 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/SchedulerProcessor.php:40
#23 Grav\Common\Processors\SchedulerProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#22 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#21 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/BackupsProcessor.php:39
#20 Grav\Common\Processors\BackupsProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#19 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#18 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/TasksProcessor.php:69
#17 Grav\Common\Processors\TasksProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#16 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#15 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/RequestProcessor.php:64
#14 Grav\Common\Processors\RequestProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#13 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#12 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/ThemesProcessor.php:38
#11 Grav\Common\Processors\ThemesProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#10 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#9 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/PluginsProcessor.php:39
#8 Grav\Common\Processors\PluginsProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#7 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#6 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Processors/InitializeProcessor.php:130
#5 Grav\Common\Processors\InitializeProcessor:Grav\Common\Processors\{closure} in /home/kociemie/SP/system/src/Grav/Common/Debugger.php:546
#4 Grav\Common\Debugger:profile in /home/kociemie/SP/system/src/Grav/Common/Processors/InitializeProcessor.php:131
#3 Grav\Common\Processors\InitializeProcessor:process in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:50
#2 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php:62
#1 Grav\Framework\RequestHandler\RequestHandler:handle in /home/kociemie/SP/system/src/Grav/Common/Grav.php:307
#0 Grav\Common\Grav:process in /home/kociemie/SP/index.php:47
```