ensure probability of gene in bmr_pmf is nonzero to avoid computing l…

…og(0) and encountering warning

src/dialect/models/gene.py

@@ -56,7 +56,7 @@ def compute_log_likelihood(self, pi):
         log_likelihood = sum(
             np.log(self.bmr_pmf.get(c, 0) * (1 - pi) + self.bmr_pmf.get(c - 1, 0) * pi)
             for c in self.counts
-            if c in self.bmr_pmf
+            if c in self.bmr_pmf and self.bmr_pmf[c] > 0
         )
         return log_likelihood