title: removeobjectAtIndex: causes index to be -1;
body: <p>I have a <code>NSTableView</code> that is populated by an array called tableArray. I have a button that is supposed to remove the selected item from the array. In my removeItem: method:</p>
  
  <pre><code>[tableArray removeObjectAtIndex:[tableView selectedRow];
  [tableView reloadData];
  </code></pre>
  
  <p>But I get the error:</p>
  
  <pre><code>2015-05-13 18:16:45.283 FileShedb1.0[979:303] *** -[__NSArrayM objectAtIndex:]: index 18446744073709551615 beyond bounds [0 .. 0]
  2015-05-13 18:16:45.288 FileShedb1.0[979:303] (
      0   CoreFoundation                      0x00007fff8d35ff56 __exceptionPreprocess + 198
      1   libobjc.A.dylib                     0x00007fff93119d5e objc_exception_throw + 43
      2   CoreFoundation                      0x00007fff8d2ed392 -[__NSArrayM objectAtIndex:] + 274
      3   FileShedb1.0                        0x00000001000028a9 -[MPOMainWindowController tableViewSelectionDidChange:] + 201
      4   Foundation                          0x00007fff8cca0d0e __-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_1 + 47
      5   CoreFoundation                      0x00007fff8d3087ba _CFXNotificationPost + 2634
      6   Foundation                          0x00007fff8cc8cfc3 -[NSNotificationCenter postNotificationName:object:userInfo:] + 65
      7   AppKit                              0x00007fff8ab10049 -[NSTableView _sendSelectionChangedNotificationForRows:columns:] + 203
      8   AppKit                              0x00007fff8aae6b0a -[NSTableView _enableSelectionPostingAndPost] + 425
      9   AppKit                              0x00007fff8aadcd75 -[NSTableView _tileAndRedisplayAll] + 358
      10  FileShedb1.0                        0x00000001000027bc -[MPOMainWindowController removeFile:] + 188
      11  CoreFoundation                      0x00007fff8d34f70d -[NSObject performSelector:withObject:] + 61
      12  AppKit                              0x00007fff8aaa98ca -[NSApplication sendAction:to:from:] + 139
      13  AppKit                              0x00007fff8aaa97fe -[NSControl sendAction:to:] + 88
      14  AppKit                              0x00007fff8aaa9729 -[NSCell _sendActionFrom:] + 137
      15  AppKit                              0x00007fff8aaa8bec -[NSCell trackMouse:inRect:ofView:untilMouseUp:] + 2014
      16  AppKit                              0x00007fff8ab28b74 -[NSButtonCell trackMouse:inRect:ofView:untilMouseUp:] + 489
      17  AppKit                              0x00007fff8aaa77f6 -[NSControl mouseDown:] + 786
      18  AppKit                              0x00007fff8aa72c98 -[NSWindow sendEvent:] + 6306
      19  AppKit                              0x00007fff8aa0c3a5 -[NSApplication sendEvent:] + 5593
      20  AppKit                              0x00007fff8a9a2a0e -[NSApplication run] + 555
      21  AppKit                              0x00007fff8ac1eeac NSApplicationMain + 867
      22  FileShedb1.0                        0x00000001000014c2 main + 34
      23  FileShedb1.0                        0x0000000100001494 start + 52
  )
  </code></pre>
  
  <p>Anyone know why i'm getting the error?</p>