Revert "[FIX] build-tracks: bug introdcued in #cc1347b" (was actually not a bug)

This reverts commit 094decd.

Author: cpockrandt

src/phylocsf++build_tracks.hpp

@@ -187,7 +187,12 @@ void run_tracks(const std::string & alignment_path, const Model & model, const T
                         // the last 0-2 remaining basepairs in the bls array do not have a codon entry
                         assert(lpr_per_codon[thread_id].size() * 3 <= bls_per_bp[thread_id].size());
 
-                        for (size_t xx = 0, bls_pos = aln.skip_bases; xx < lpr_per_codon[thread_id].size(); ++xx, bls_pos += 3)
+                        size_t bls_pos;
+                        if (strand == '+')
+                            bls_pos = aln.skip_bases;
+                        else
+                            bls_pos = aln.length() % 3;
+                        for (size_t xx = 0; xx < lpr_per_codon[thread_id].size(); ++xx, bls_pos += 3)
                         {
                             const float bls_codon_sum = bls_per_bp[thread_id][bls_pos]
                                                         + bls_per_bp[thread_id][bls_pos + 1]