[Bug Fix] Edge case: BitSet when highest bit index is a multiplication of 32 (#10)

* [Bug Fix] Edge case of bit index which has no residue when dividing with 32 (From last bit index to bit array length: +1)

* [Code Review] Fixed according to code review

* [Test] Simple values test fixed

Author: yanivshaked

lib/src/bit_set.dart

@@ -108,7 +108,7 @@ class ListSet extends BitSet {
   }
 
   @override
-  int get length => _list.isEmpty ? 0 : _list.last;
+  int get length => _list.isEmpty ? 0 : _list.last + 1;
 
   @override
   int get cardinality {

test/bit_counter_test.dart

@@ -99,6 +99,12 @@ void main() {
       expect(counter[2001], 0);
     });
 
+    test('bit sets (edge case)', () {
+      final counter = BitCounter(0);
+      counter.addBitSet(ListSet.fromSorted([0, 2, 5, 2048]));
+      expect(counter[2048], 1);
+    });
+
     test('bit set with shift', () {
       final counter = BitCounter(128);
       counter.addBitSet(ListSet.fromSorted([0, 2, 5]), shiftLeft: 3);

test/bit_set_test.dart

@@ -7,7 +7,7 @@ void main() {
     final set = ListSet.fromSorted([23, 45, 78, 98, 101, 102, 103]);
 
     test('simple values', () {
-      expect(set.length, 103);
+      expect(set.length, 104);
       expect(set.cardinality, 7);
       expect(set[22], isFalse);
       expect(set[23], isTrue);