From 8a2d361aa63bc434d1e8c0bc92677eee5aa0f0af Mon Sep 17 00:00:00 2001
From: Thomas Van Lenten <thomasvl@google.com>
Date: Fri, 6 Oct 2017 13:12:48 -0400
Subject: Under iOS 11, CFRelease doesn't seem to like releasing nil?

---
 AddressBook/GTMABAddressBook.m | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/AddressBook/GTMABAddressBook.m b/AddressBook/GTMABAddressBook.m
index d92cb08..4a7d733 100644
--- a/AddressBook/GTMABAddressBook.m
+++ b/AddressBook/GTMABAddressBook.m
@@ -100,7 +100,9 @@ typedef struct {
   if (!wasGood) {
     _GTMDevLog(@"Error in [%@ %@]: %@",
                [self class], NSStringFromSelector(_cmd), cfError);
-    CFRelease(cfError);
+    if (cfError) {
+      CFRelease(cfError);
+    }
   }
 #else  // GTM_IPHONE_SDK
   bool wasGood = ABSave(addressBook_);
-- 
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