use the empty string instead of null as an array offset (#12181)

Author: xabbuh

src/Persisters/Entity/JoinedSubclassPersister.php

@@ -63,7 +63,7 @@ protected function getDiscriminatorColumnTableName()
      */
     private function getVersionedClassMetadata(): ClassMetadata
     {
-        if (isset($this->class->fieldMappings[$this->class->versionField]['inherited'])) {
+        if ($this->class->versionField !== null && isset($this->class->fieldMappings[$this->class->versionField]['inherited'])) {
             $definingClassName = $this->class->fieldMappings[$this->class->versionField]['inherited'];
 
             return $this->em->getClassMetadata($definingClassName);

src/Query/ResultSetMappingBuilder.php

@@ -411,7 +411,7 @@ public function addNamedNativeQueryEntityResultMapping(ClassMetadataInfo $classM
                     [$relation, $fieldName] = explode('.', $fieldName);
                 }
 
-                if (isset($classMetadata->associationMappings[$relation])) {
+                if ($relation !== null && isset($classMetadata->associationMappings[$relation])) {
                     if ($relation) {
                         $associationMapping = $classMetadata->associationMappings[$relation];
                         $joinAlias          = $alias . $relation;

src/Query/SqlWalker.php

@@ -1587,7 +1587,9 @@ public function walkSelectExpression($selectExpression)
 
                     $sqlParts[] = $col . ' AS ' . $columnAlias;
 
-                    $this->scalarResultAliasMap[$resultAlias][] = $columnAlias;
+                    if ($resultAlias !== null) {
+                        $this->scalarResultAliasMap[$resultAlias][] = $columnAlias;
+                    }
 
                     $this->rsm->addFieldResult($dqlAlias, $columnAlias, $fieldName, $class->name);
 
@@ -1622,7 +1624,9 @@ public function walkSelectExpression($selectExpression)
 
                             $sqlParts[] = $col . ' AS ' . $columnAlias;
 
-                            $this->scalarResultAliasMap[$resultAlias][] = $columnAlias;
+                            if ($resultAlias !== null) {
+                                $this->scalarResultAliasMap[$resultAlias][] = $columnAlias;
+                            }
 
                             $this->rsm->addFieldResult($dqlAlias, $columnAlias, $fieldName, $subClassName);
                         }

src/Tools/Pagination/LimitSubqueryOutputWalker.php

@@ -149,7 +149,9 @@ private function rebuildOrderByForRowNumber(SelectStatement $AST): void
         $selectAliasToExpressionMap = [];
         // Get any aliases that are available for select expressions.
         foreach ($AST->selectClause->selectExpressions as $selectExpression) {
-            $selectAliasToExpressionMap[$selectExpression->fieldIdentificationVariable] = $selectExpression->expression;
+            if ($selectExpression->fieldIdentificationVariable !== null) {
+                $selectAliasToExpressionMap[$selectExpression->fieldIdentificationVariable] = $selectExpression->expression;
+            }
         }
 
         // Rebuild string orderby expressions to use the select expression they're referencing