Fix BitVector::SetInitialBits().

Change-Id: Iad3699d76ad69536aa4810329f5863bc995f6551
diff --git a/runtime/base/bit_vector.cc b/runtime/base/bit_vector.cc
index 3db8e12..590835e 100644
--- a/runtime/base/bit_vector.cc
+++ b/runtime/base/bit_vector.cc
@@ -265,6 +265,7 @@
   uint32_t rem_num_bits = num_bits & 0x1f;
   if (rem_num_bits != 0) {
     storage_[idx] = (1 << rem_num_bits) - 1;
+    ++idx;
   }
 
   // Now set the upper ones to 0.