I get error when I add a UITableView

I have a static UITableView, and in one of the cells, I have a dynamic UITableView. Here is the code I used:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell;

    if (self.tableView == tableView) {
        cell = [tableView cellForRowAtIndexPath:indexPath];
    }
    else {
        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell" forIndexPath:indexPath];
        [cell.textLabel setText:self.tagsArray [indexPath.row]];
    }
    return cell;
}

When I run the app, it crashes with the following error:

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath:'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000106efbc65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x0000000106b94bb7 objc_exception_throw + 45
    2   CoreFoundation                      0x0000000106efbaca +[NSException raise:format:arguments:] + 106
    3   Foundation                          0x00000001067a998f -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 195
    4   UIKit                               0x000000010762fa83 -[UITableView _configureCellForDisplay:forIndexPath:] + 128
    5   UIKit                               0x0000000107637a41 -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] + 533
    6   UIKit                               0x0000000107616248 -[UITableView _updateVisibleCellsNow:isRecursive:] + 2853
    7   UIKit                               0x000000010762c8a9 -[UITableView layoutSubviews] + 210
    8   UIKit                               0x00000001075b6a2b -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 536
    9   QuartzCore                          0x0000000106588ec2 -[CALayer layoutSublayers] + 146
    10  QuartzCore                          0x000000010657d6d6 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380
    11  QuartzCore                          0x000000010657d546 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
    12  QuartzCore                          0x00000001064e9886 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 242
    13  QuartzCore                          0x00000001064eaa3a _ZN2CA11Transaction6commitEv + 462
    14  QuartzCore                          0x00000001064eb0eb _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 89
    15  CoreFoundation                      0x0000000106e2eca7 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
    16  CoreFoundation                      0x0000000106e2ec00 __CFRunLoopDoObservers + 368
    17  CoreFoundation                      0x0000000106e24a33 __CFRunLoopRun + 1123
    18  CoreFoundation                      0x0000000106e24366 CFRunLoopRunSpecific + 470
    19  GraphicsServices                    0x000000010ad61a3e GSEventRunModal + 161
    20  UIKit                               0x0000000107536900 UIApplicationMain + 1282
    21  myBudget                            0x000000010611fe5f main + 111
    22  libdyld.dylib                       0x0000000108952145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Why do I get this error, and what can I do to fix it?