fix PHP8.5 deprecation - Using null as an array offset is deprecated, use an empty string instead

Author: aaa2000

src/Doctrine/Odm/Filter/ExistsFilter.php

@@ -129,7 +129,7 @@ public function __construct(?ManagerRegistry $managerRegistry = null, ?LoggerInt
     public function apply(Builder $aggregationBuilder, string $resourceClass, ?Operation $operation = null, array &$context = []): void
     {
         $parameter = $context['parameter'] ?? null;
-        if (null !== ($value = $context['filters'][$parameter?->getProperty()] ?? null)) {
+        if (null !== ($value = $context['filters'][$parameter?->getProperty() ?? ''] ?? null)) {
             $this->filterProperty($this->denormalizePropertyName($parameter->getProperty()), $value, $aggregationBuilder, $resourceClass, $operation, $context);
 
             return;

src/Doctrine/Odm/Filter/OrderFilter.php

@@ -239,7 +239,7 @@ public function apply(Builder $aggregationBuilder, string $resourceClass, ?Opera
         }
 
         $parameter = $context['parameter'] ?? null;
-        if (null !== ($value = $context['filters'][$parameter?->getProperty()] ?? null)) {
+        if (null !== ($value = $context['filters'][$parameter?->getProperty() ?? ''] ?? null)) {
             $this->filterProperty($this->denormalizePropertyName($parameter->getProperty()), $value, $aggregationBuilder, $resourceClass, $operation, $context);
 
             return;

src/Doctrine/Orm/Filter/ExistsFilter.php

@@ -136,7 +136,7 @@ public function apply(QueryBuilder $queryBuilder, QueryNameGeneratorInterface $q
     {
         $parameter = $context['parameter'] ?? null;
 
-        if (null !== ($value = $context['filters'][$parameter?->getProperty()] ?? null)) {
+        if (null !== ($value = $context['filters'][$parameter?->getProperty() ?? ''] ?? null)) {
             $this->filterProperty($this->denormalizePropertyName($parameter->getProperty()), $value, $queryBuilder, $queryNameGenerator, $resourceClass, $operation, $context);
 
             return;

src/Doctrine/Orm/Filter/OrderFilter.php

@@ -238,7 +238,7 @@ public function apply(QueryBuilder $queryBuilder, QueryNameGeneratorInterface $q
         }
 
         $parameter = $context['parameter'] ?? null;
-        if (null !== ($value = $context['filters'][$parameter?->getProperty()] ?? null)) {
+        if (null !== ($value = $context['filters'][$parameter?->getProperty() ?? ''] ?? null)) {
             $this->filterProperty($this->denormalizePropertyName($parameter->getProperty()), $value, $queryBuilder, $queryNameGenerator, $resourceClass, $operation, $context);
 
             return;