Fix static analysis error

Author: mpdude

lib/Doctrine/ORM/Tools/SchemaValidator.php

@@ -253,7 +253,7 @@ public function validateClass(ClassMetadataInfo $class)
             }
         }
 
-        if (! $class->isInheritanceTypeNone() && ! $class->isRootEntity() && ! $class->reflClass->isAbstract() && ! $class->isMappedSuperclass && array_search($class->name, $class->discriminatorMap, true) === false) {
+        if (! $class->isInheritanceTypeNone() && ! $class->isRootEntity() && ($class->reflClass !== null && ! $class->reflClass->isAbstract()) && ! $class->isMappedSuperclass && array_search($class->name, $class->discriminatorMap, true) === false) {
             $ce[] = "Entity class '" . $class->name . "' is part of inheritance hierarchy, but is " .
                 "not mapped in the root entity '" . $class->rootEntityName . "' discriminator map. " .
                 'All subclasses must be listed in the discriminator map.';