diff --git a/core/modules/views/src/Plugin/views/argument_validator/Entity.php b/core/modules/views/src/Plugin/views/argument_validator/Entity.php
index ba0bb219623d12b03f03fbb4aac660b5c8ac0e0c..1954a10c56c08848b4ea37ce6932f7ce102bc888 100644
--- a/core/modules/views/src/Plugin/views/argument_validator/Entity.php
+++ b/core/modules/views/src/Plugin/views/argument_validator/Entity.php
@@ -177,7 +177,7 @@ public function submitOptionsForm(&$form, FormStateInterface $form_state, &$opti
   public function validateArgument($argument) {
     $entity_type = $this->definition['entity_type'];
 
-    if ($this->multipleCapable && $this->options['multiple']) {
+    if ($this->multipleCapable && $this->options['multiple'] && isset($argument)) {
       // At this point only interested in individual IDs no matter what type,
       // just splitting by the allowed delimiters.
       $ids = array_filter(preg_split('/[,+ ]/', $argument));
diff --git a/core/modules/views/tests/src/Unit/Plugin/argument_validator/EntityTest.php b/core/modules/views/tests/src/Unit/Plugin/argument_validator/EntityTest.php
index b7ccfa001980fd1edc5a4dce8bc91f661bd8b806..0b021fd61d885df8d5a52a50a8238881e7652bbb 100644
--- a/core/modules/views/tests/src/Unit/Plugin/argument_validator/EntityTest.php
+++ b/core/modules/views/tests/src/Unit/Plugin/argument_validator/EntityTest.php
@@ -129,6 +129,7 @@ public function testValidateArgumentNoAccess() {
 
     $this->assertFalse($this->argumentValidator->validateArgument(3));
     $this->assertFalse($this->argumentValidator->validateArgument(''));
+    $this->assertFalse($this->argumentValidator->validateArgument(NULL));
 
     $this->assertTrue($this->argumentValidator->validateArgument(1));
     $this->assertTrue($this->argumentValidator->validateArgument(2));
@@ -249,6 +250,8 @@ public function testValidateArgumentMultiple() {
     $this->assertFalse($this->argumentValidator->validateArgument('1,2'));
     $this->assertFalse($this->argumentValidator->validateArgument('1+2'));
 
+    $this->assertFalse($this->argumentValidator->validateArgument(NULL));
+
     $options = [];
     $options['access'] = TRUE;
     $options['bundles'] = [];