Replace usage of null as array offset

ref: https://www.php.net/manual/en/migration85.deprecated.php#migration85.deprecated.core.using-null-as-an-array-offset

Author: Jan-Schuppik

src/FormElement/SelectElement.php

@@ -32,7 +32,7 @@ class SelectElement extends BaseFormElement
     /**
      * Get the option with specified value
      *
-     * @param string|int|null $value
+     * @param string|int $value
      *
      * @return ?SelectOption
      */
@@ -119,7 +119,7 @@ public function getNameAttribute()
     /**
      * Make the selectOption for the specified value and the label
      *
-     * @param string|int|null $value Value of the option
+     * @param string|int $value Value of the option
      * @param string|array $label Label of the option
      *
      * @return SelectOption|HtmlElement

tests/DocumentationFormsTest.php

@@ -25,7 +25,7 @@ public function testSelectElement()
         $form->addElement('select', 'customer', [
             'label'   => 'Customer',
             'options' => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',
@@ -57,7 +57,7 @@ public function testSetValues()
         $form->addElement('select', 'customer', [
             'label'   => 'Customer',
             'options' => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',

tests/FormElement/FieldsetElementTest.php

@@ -15,7 +15,7 @@
 class FieldsetElementTest extends TestCase
 {
     private const SELECT_OPTIONS_TO_TEST = [
-        null  => 'Nothing',
+        ''    => 'Nothing',
         1     => 'One',
         'two' => 2,
     ];

tests/FormElement/SelectElementTest.php

@@ -17,7 +17,7 @@ public function testFlatOptions()
         $select = new SelectElement('elname', [
             'label'   => 'Customer',
             'options' => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',
@@ -43,7 +43,7 @@ public function testOptionValidity()
             'label'   => 'Customer',
             'value'   => '3',
             'options' => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',
@@ -72,7 +72,7 @@ public function testSelectingDisabledOptionIsNotPossible()
             'label'   => 'Customer',
             'value'   => '4',
             'options' => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',
@@ -93,7 +93,7 @@ public function testNestedOptions()
         $select = new SelectElement('elname', [
             'label'   => 'Customer',
             'options' => [
-                null => 'Please choose',
+                '' => 'Please choose',
                 'Some Options' => [
                     '1'  => 'The one',
                     '4'  => 'Four',
@@ -125,7 +125,7 @@ public function testDisabledNestedOptions()
         $select = new SelectElement('elname', [
             'label'   => 'Customer',
             'options' => [
-                null => 'Please choose',
+                '' => 'Please choose',
                 'Some options' => [
                     '1'  => 'The one',
                     '4'  => 'Four',
@@ -160,7 +160,7 @@ public function testDeeplyDisabledNestedOptions()
         $select = new SelectElement('elname', [
             'label'   => 'Customer',
             'options' => [
-                null => 'Please choose',
+                '' => 'Please choose',
                 'Some options' => [
                     '1'  => 'The one',
                     '4'  => [
@@ -204,7 +204,7 @@ public function testDefaultValueIsSelected()
             'label'   => 'Customer',
             'value'   => '1',
             'options' => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',
@@ -228,7 +228,7 @@ public function testSetValueSelectsAnOption()
         $select = new SelectElement('elname', [
             'label'   => 'Customer',
             'options' => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',
@@ -280,7 +280,7 @@ public function testSetArrayAsValueWithoutMultipleAttributeThrowsException()
         $select = new SelectElement('elname', [
             'label'     => 'Customer',
             'options'   => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',
@@ -301,7 +301,7 @@ public function testSetNonArrayAsValueWithMultipleAttributeThrowsException()
             'label'     => 'Customer',
             'multiple'  => true,
             'options'   => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',
@@ -323,7 +323,7 @@ public function testSetArrayAsValueWithMultipleAttributeSetTheOptions()
         $select = new SelectElement('elname', [
             'label'   => 'Customer',
             'options' => [
-                null => 'Please choose',
+                ''   => 'Please choose',
                 '1'  => 'The one',
                 '4'  => 'Four',
                 '5'  => 'Hi five',