MathEditor Error when trying to edit Matrix

So I was working on making it possible, so that you could insert an editable Matrix in your editable math label. What I did was inserting this code into MTEditableMathLabel:

`- (void) insertMatrix: (int)rows :(int)columns :(NSString )type { MTMathAtom atom = [MTMathAtomFactory placeholderMatrix:columns :rows :type];

if (_insertionIndex.subIndexType == kMTSubIndexTypeDenominator) {
    if (atom.type == kMTMathAtomRelation) {
        // pull the insertion index out
        _insertionIndex = [[_insertionIndex levelDown] next];
    }
}

if (atom) {
    if (![self updatePlaceholderIfPresent:atom]) {
        // If a placeholder wasn't updated then insert the new element.
        [self.mathList insertAtom:atom atListIndex:_insertionIndex];
    }
    if (atom.type == kMTMathAtomFraction) {
        // go to the numerator
        _insertionIndex = [_insertionIndex levelUpWithSubIndex:[MTMathListIndex level0Index:0] type:kMTSubIndexTypeNumerator];
    } else {
        _insertionIndex = _insertionIndex.next;
    }
}

self.label.mathList = self.mathList;
[self insertionPointChanged];

if ([self.delegate respondsToSelector:@selector(textModified:)]) {
    [self.delegate textModified:self];
}

}`

and this code into MTMathAtomFactory

`+ (MTMathAtom *)placeholderMatrix: (int)width :(int)height :(NSString )envname { NSError error;

NSMutableArray<NSMutableArray<MTMathList*>*>* rows = [[NSMutableArray alloc] initWithCapacity:(NSInteger)height];
for (int y = 0; y < height; y++)
{
    NSMutableArray<MTMathList*>* row = [[NSMutableArray alloc] initWithCapacity:(NSInteger)width];
    
    for (int x = 0; x < width; x++)
    {
        MTMathList* list = [MTMathList new];
        
        [list addAtom:[self placeholder]];
        
        row[x] = list;
    }
    
    rows[y] = row;
}
MTMathAtom* table = [MTMathAtomFactory tableWithEnvironment:envname rows:rows error:&error];

return table;

}`

This displays the matrix fine, but when I try to select one of the Values in the matrix I get this error, which I have no idea where it is coming from.

'MTLine type regular inside an MTLine - shouldn't happen'

But the display is exactly the way I want it to be. What is wrong here ? I really need help on this please. Thanks a lot for any help in advance.