NSTextAlignmentJustified exception with arabic string

Question

I am using Arabic string and I want to justify it inside UITextView.

I am retrieving incoming attributingString in the textView and enumerate the NSParagraphStyleAttributeName to edit it like this :

NSMutableAttributedString * mstring = [[NSMutableAttributedString alloc] initWithAttributedString:_textView.attributedText];

[_textView.attributedText enumerateAttribute:NSParagraphStyleAttributeName inRange:NSMakeRange(0, _textView.attributedText.length) options:0
                                  usingBlock:^(id value, NSRange range, BOOL *stop) {
                                      NSMutableParagraphStyle * paragraphStyle = (NSMutableParagraphStyle *)value;
                                      if (paragraphStyle.alignment == NSTextAlignmentRight) {


                                          paragraphStyle.lineBreakMode = NSLineBreakByWordWrapping;
                                          paragraphStyle.alignment = NSTextAlignmentJustified;
                                          paragraphStyle.baseWritingDirection = NSWritingDirectionRightToLeft;
                                          [mstring addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:range];
                                          [self.textView setAttributedText:mstring];
                                      }


}];

I found that, if the attributed string is Arabic, the application crashed, but if it is English, it is working normally.

Any ideas to solve this problem?