Remove "empty" character from String

I'm using a framwork which returns malformed Strings with "empty" characters from time to time.

"foobar" for example is represented by: [,f,o,o,b,a,r]

The first character is NOT a whitespace (' '), so a System.out.printlin() would return "foobar" and not " foobar". Yet, the length of the String is 7 instead of 6. Obviously this makes most String methods (equals, split, substring,..) useless. Is there a way to remove empty characters from a String?

I tried to build a new String like this:

StringBuilder sb = new StringBuilder();
for (final char character : malformedString.toCharArray()) {
  if (Character.isDefined(character)) {
    sb.append(character);
  }
}
sb.toString();

Unfortunately this doesn't work. Same with the following code:

StringBuilder sb = new StringBuilder();
for (final Character character : malformedString.toCharArray()) {
  if (character != null) {
    sb.append(character);
  }
}
sb.toString();

I also can't check for an empty character like this:

   if (character == ''){
     //
   }

Obviously there is something wrong with the String .. but I can't change the framework I'm using or wait for them to fix it (if it is a bug within their framework). I need to handle this String and sanatize it.

Any ideas?