Failure on rendering \sqrt{} command

[nuixdt]

If the latex is \sqrt only, it will crash on getNextCharacter function call. We modify the sqrt command to check the array index and length by hasCharacters function in MTMathListBuilder.m

• (MTMathAtom*) atomForCommand:(NSString*) command
  {
  ......
  } else if ([command isEqualToString:@"sqrt"]) {
  // A sqrt command with one argument
  MTRadical* rad = [MTRadical new];
  if ([self hasCharacters]) {
  unichar ch = [self getNextCharacter];
  if (ch == '[') {
  // special handling for sqrt[degree]{radicand}
  rad.degree = [self buildInternal:false stopChar:']'];
  rad.radicand = [self buildInternal:true];
  } else {
  [self unlookCharacter];
  rad.radicand = [self buildInternal:true];
  }
  }
  return rad;