App crashes when access the length of [NSData dataWithContentsOfURL:url]
<p>Here is the problem:</p>

<p>The app crashes at the 2nd line, and I got EXC_BAD_ACCESS exception.</p>

<pre><code>NSURL *url = [NSURL URLWithString:@"..."];

NSError *error = nil;
NSData *data = [NSData dataWithContentsOfURL:url 
          options:NSDataReadingMapped 
            error:&amp;error];
NSLog(@"Error: %@", error);
NSLog(@"%@", [data length]);
</code></pre>

<p>I got:</p>

<pre><code>Error: (null)
Program received signal:  “EXC_BAD_ACCESS”.
</code></pre>

<p>Any idea?</p>
