psalm: PHP Fatal error: Uncaught TypeError: Argument 3 passed to Psalm\Checker\TypeChecker::isContainedBy() must be an instance of Psalm\Type\Union, null given,

Trying to run Psalm on the LimeSurvey project, I received these errors:

PHP Notice:  Undefined offset: 2 in /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php on line 369

Notice: Undefined offset: 2 in /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php on line 369
PHP Fatal error:  Uncaught TypeError: Argument 3 passed to Psalm\Checker\TypeChecker::isContainedBy() must be an instance of Psalm\Type\Union, null given, called in /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php on line 380 and defined in /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php:43
Stack trace:
#0 /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php(380): Psalm\Checker\TypeChecker::isContainedBy(Object(Psalm\Codebase), Object(Psalm\Type\Union), NULL, false, false, true, NULL, NULL)
#1 /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php(86): Psalm\Checker\TypeChecker::isAtomicContainedBy(Object(Psalm\Codebase), Object(Psalm\Type\Atomic\TArray), Object(Psalm\Type\Atomic\TArray), true, NULL, NULL, false)
#2 /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/FunctionLikeChecker.php(971): Psalm\Checker\TypeChecker::isContainedBy(Object(Psalm\Codebase), Object(Psalm\Type in /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php on line 43

Fatal error: Uncaught TypeError: Argument 3 passed to Psalm\Checker\TypeChecker::isContainedBy() must be an instance of Psalm\Type\Union, null given, called in /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php on line 380 and defined in /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php:43
Stack trace:
#0 /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php(380): Psalm\Checker\TypeChecker::isContainedBy(Object(Psalm\Codebase), Object(Psalm\Type\Union), NULL, false, false, true, NULL, NULL)
#1 /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php(86): Psalm\Checker\TypeChecker::isAtomicContainedBy(Object(Psalm\Codebase), Object(Psalm\Type\Atomic\TArray), Object(Psalm\Type\Atomic\TArray), true, NULL, NULL, false)
#2 /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/FunctionLikeChecker.php(971): Psalm\Checker\TypeChecker::isContainedBy(Object(Psalm\Codebase), Object(Psalm\Type in /limesurvey/third_party/vimeo/psalm/src/Psalm/Checker/TypeChecker.php on line 43

Any idea for a next step?