Probabilities do not sum to 1
While running recent version of the code, I've hit this error. 

```
  File "/home/skoposov/pyenv38/lib/python3.8/site-packages/dynesty/dynamicsampler.py", line 1596, in run_nested
    passback = self.add_batch(nlive=nlive_batch,
  File "/home/skoposov/pyenv38/lib/python3.8/site-packages/dynesty/dynamicsampler.py", line 1716, in add_batch
    for results in self.sample_batch(nlive_new=nlive,
  File "/home/skoposov/pyenv38/lib/python3.8/site-packages/dynesty/dynamicsampler.py", line 1054, in sample_batch
    subset = self.rstate.choice(np.nonzero(subset)[0],
  File "mtrand.pyx", line 933, in numpy.random.mtrand.RandomState.choice
ValueError: probabilities do not sum to 1
```
which was recently introduced code

I haven't had a chance to investigate this.  I'm guessing it has to do with very large/small/inf values in logwt



diff --git a/py/dynesty/dynamicsampler.py b/py/dynesty/dynamicsampler.py
index 8ee5315..216adee 100644
--- a/py/dynesty/dynamicsampler.py
+++ b/py/dynesty/dynamicsampler.py
@@ -1043,7 +1043,11 @@ class DynamicSampler(object):
             # we are weighting each point by 1/L_i * 1/W_i to ensure
             # uniform sampling within boundary volume
             cur_logwt = -saved_logl[subset] - saved_logwt[subset]
-            cur_wt = np.exp(cur_logwt - logsumexp(cur_logwt))
+            cur_wt = np.exp(cur_logwt - cur_logwt.max())
+            cur_wt = cur_wt / cur_wt.sum()
+            # i normalize in linear space rather then using logsumexp
+            # because cur_wt.sum() needs to be 1 for random.choice
+
             # we are now randomly sampling with weights
             # notice that since we are samplign without
             # replacement we aren't guaranteed to be able
['py/dynesty/dynamicsampler.py']