Fatal error upon creating new journal issue

[Vitaliy-1]

Tested with OJS 3.1.2 and the current master branch of the Immersion theme.
Associated PHP error:

PHP Fatal error:  Uncaught Error: Call to a member function getId() on null in /var/www/ojs-3.1.2/plugins/themes/immersion/ImmersionThemePlugin.inc.php:320
Stack trace:
#0 /var/www/ojs-3.1.2/lib/pkp/classes/plugins/HookRegistry.inc.php(107): ImmersionThemePlugin->addToIssueForm('issueform::disp...', Array)
#1 /var/www/ojs-3.1.2/lib/pkp/classes/form/Form.inc.php(174): HookRegistry::call('issueform::disp...', Array)
#2 /var/www/ojs-3.1.2/controllers/grid/issues/form/IssueForm.inc.php(94): Form->fetch(Object(Request))
#3 /var/www/ojs-3.1.2/classes/controllers/grid/issues/IssueGridHandler.inc.php(160): IssueForm->fetch(Object(Request))
#4 /var/www/ojs-3.1.2/classes/controllers/grid/issues/IssueGridHandler.inc.php(132): IssueGridHandler->editIssueData(Array, Object(Request))
#5 /var/www/ojs-3.1.2/lib/pkp/classes/core/PKPRouter.inc.php(390): IssueGridHandler->addIssue(Array, Object(Request))
#6 /var/www/ojs-3.1.2/lib/pkp/classes/core/PKPComponentRouter.inc.php(257): PKPRouter->_authorizeInitializeAndCallRequest(Array, Object(Request in /var/www/ojs-3.1.2/plugins/themes/immersion/ImmersionThemePlugin.inc.php on line 320