Fixed string conversions to avoid nil pointers.

base/ios/device_util.mm

Index: base/ios/device_util.mm
diff --git a/base/ios/device_util.mm b/base/ios/device_util.mm
index 84495377c547340f30685ca339bb817832776179..c3e9c2079fe5a92ad03f0c15952893af52c78d99 100644
--- a/base/ios/device_util.mm
+++ b/base/ios/device_util.mm
@@ -46,7 +46,7 @@ NSString* GenerateClientId() {
   if (!client_id || [client_id isEqualToString:kZeroUUID]) {
     if (base::ios::IsRunningOnIOS6OrLater()) {
       client_id = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
-      if ([client_id isEqualToString:kZeroUUID])
+      if (!client_id || [client_id isEqualToString:kZeroUUID])
         client_id = base::SysUTF8ToNSString(ios::device_util::GetRandomId());
     } else {
       client_id = base::SysUTF8ToNSString(ios::device_util::GetRandomId());
@@ -157,16 +157,16 @@ std::string GetDeviceIdentifier(const char* salt) {
     [defaults synchronize];
   }
 
-  return GetSaltedString([client_id UTF8String], salt ? salt : kDefaultSalt);
+  return GetSaltedString(base::SysNSStringToUTF8(client_id),
+                         salt ? salt : kDefaultSalt);
 }
 
 std::string GetSaltedString(const std::string& in_string,
                             const std::string& salt) {
   DCHECK(in_string.length());
   DCHECK(salt.length());
-  NSData* hash_data =
-      [[NSString stringWithFormat:@"%s%s", in_string.c_str(), salt.c_str()]
-          dataUsingEncoding:NSUTF8StringEncoding];
+  NSData* hash_data = [base::SysUTF8ToNSString(in_string + salt)
+      dataUsingEncoding:NSUTF8StringEncoding];
 
   unsigned char hash[CC_SHA256_DIGEST_LENGTH];
   CC_SHA256([hash_data bytes], [hash_data length], hash);