title: Check if NSDictionary is empty
body: <p>I want to check if an <code>NSDictionary</code> is empty. I am doing it like this.</p>
  
  <pre><code>  mutDictValues = [[[NSUserDefaults standardUserDefaults] objectForKey:@"dicValues"]mutableCopy];
      NSLog(@"dictValues are %@",mutDictValues);
      if(mutDictValues == NULL){
          arrCities = [[NSMutableArray alloc]init];
          NSLog(@"no cities seleceted");
      }else{
            arrCities = [[NSMutableArray alloc]init];
            arrCities = [mutDictValues objectForKey:@"cities"];
            [self placeCities];
      }
  </code></pre>
  
  <p>But it alwasy crashes on this line <code>arrCities = [mutDictValues objectForKey:@"cities"];</code> with the following error:</p>
  
  <pre><code>-[__NSCFConstantString objectForKey:]:
  </code></pre>
  
  <p>Can someone help me with this ?</p>