Add missing NULL checks for spl autoload table

Closes GH-12840.

NEWS

@@ -9,6 +9,7 @@ PHP                                                                        NEWS
     php_message_handler_for_zend). (ilutov)
   . Fixed bug GH-12758 / GH-12768 (Invalid opline in OOM handlers within
     ZEND_FUNC_GET_ARGS and ZEND_BIND_STATIC). (Florian Engelhardt)
+  . Fix various missing NULL checks. (nielsdos, dstogov)
 
 - Date:
   . Fixed improbably integer overflow while parsing really large (or small)

ext/spl/php_spl.c

@@ -585,8 +585,10 @@ PHP_FUNCTION(spl_autoload_unregister)
 
 	if (fcc.function_handler && zend_string_equals_literal(
 			fcc.function_handler->common.function_name, "spl_autoload_call")) {
-		/* Don't destroy the hash table, as we might be iterating over it right now. */
-		zend_hash_clean(spl_autoload_functions);
+		if (spl_autoload_functions) {
+			/* Don't destroy the hash table, as we might be iterating over it right now. */
+			zend_hash_clean(spl_autoload_functions);
+		}
 		RETURN_TRUE;
 	}
 

ext/spl/tests/spl_autoload_unregister_without_registrations.phpt

@@ -0,0 +1,10 @@
+--TEST--
+spl_autoload_unregister("spl_autoload_call") without registrations
+--FILE--
+<?php
+var_dump(spl_autoload_unregister("spl_autoload_call"));
+?>
+Done
+--EXPECT--
+bool(true)
+Done