NSRangeException Out of Bounds error

Question

I am setting the attributed text of a label, and I am getting this strange error: Terminating app due to uncaught exception 'NSRangeException', reason: 'NSMutableRLEArray replaceObjectsInRange:withObject:length:: Out of bounds'. I have never seen this error before, so I am not sure how to fix it. Here is the code causing the crash:

if ([cell.waveTextLabel respondsToSelector:@selector(setAttributedText:)])
{
    const CGFloat fontSize = 16.0f;

    //define attributes
    UIFont *boldFont = [UIFont fontWithName:@"HelveticaNeue-Medium" size:fontSize];

    // Create the attributes
    NSDictionary *attrs = [NSDictionary dictionaryWithObjectsAndKeys:boldFont, NSFontAttributeName, nil];

    NSRange rangeOfIs = [cell.cellWaveObject.waveString rangeOfString:@" is"];
    NSLog(@"The range of is: {%lu, %lu}", (unsigned long)rangeOfIs.location, (unsigned long)rangeOfIs.length);
    NSRange nameRange = NSMakeRange(0, rangeOfIs.location);
    NSLog(@"The range of the name: {%lu, %lu}", (unsigned long)nameRange.location, (unsigned long)nameRange.length);

    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:cell.cellWaveObject.waveString];
    [attributedString setAttributes:attrs range:nameRange];

    //set the label text
    [cell.waveTextLabel setAttributedText:attributedString]; 
}

I set a exception breakpoint, and it is crashing on the line [attributedString setAttributes:attrs range:nameRange]; does anyone know how I can fix this?