Issue #3492419 by liam morland, nickdickinsonwilde, ekes: Nullable types must be explicit

...c/Plugin/paragraphs/Conversion/ParagraphsDemoUserText.php

...in/paragraphs/Conversion/ParagraphsDemoUserToTextUser.php

...raphs_type_permissions/paragraphs_type_permissions.module

src/ParagraphsConversionBase.php

src/ParagraphsConversionInterface.php

src/ParagraphsConversionManager.php

src/Plugin/Field/FieldWidget/ParagraphsWidget.php

src/Plugin/migrate/process/ParagraphsLookup.php

...n/paragraphs/Conversion/ParagraphsTestTextToTextImage.php