修复传值类型错误。Review by 硬币。

@@ -418,7 +418,7 @@ static NSString * const kYohoBuyUsedDevice = @"com.yoho.buy.useddevice";
     if (yohoinfoKVPairs == nil || yohoinfoKVPairs[kYohoBuyUsedDevice] == nil) {
         return YES;
     } else {
-        usedDevice = yohoinfoKVPairs[kYohoBuyUsedDevice];
+        usedDevice = [NSString stringWithString:yohoinfoKVPairs[kYohoBuyUsedDevice]];
         return NO;
     }
 }