GMM Test fails when debug is enabled

# ./waf configure --enable-debug
(snip)
# ./waf --check
(snip)
  tests that fail 1/137 
    /home/subaru/jubatus/jubatus_core/build/jubatus/core/clustering/clustering_gmm_test 
Running main() from gtest_main.cc
[==========] Running 3 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 3 tests from gmm_test
[ RUN      ] gmm_test.centers_and_covs
[       OK ] gmm_test.centers_and_covs (187 ms)
[ RUN      ] gmm_test.nearest_center
[       OK ] gmm_test.nearest_center (19 ms)
[ RUN      ] gmm_test.clear_with_empty_list

/usr/include/c++/4.8/debug/vector:353:error: attempt to subscript container 
    with out-of-bounds index 0, but container only holds 0 elements.

Objects involved in the operation:
sequence "this" @ 0x0x249c840 {
  type = NSt7__debug6vectorIN5Eigen12SparseVectorIdLi0EiEESaIS3_EEE;
}

test failed

jubatus / jubatus_core

GMM Test fails when debug is enabled #91