Fix setting initvals on ZeroSumTransform rv

Author: velochy

pymc/distributions/transforms.py

@@ -300,7 +300,7 @@ def __init__(self, zerosum_axes):
 
     @staticmethod
     def extend_axis(array, axis):
-        n = (array.shape[axis] + 1).astype("floatX")
+        n = pt.cast(array.shape[axis] + 1, "floatX")
         sum_vals = array.sum(axis, keepdims=True)
         norm = sum_vals / (pt.sqrt(n) + n)
         fill_val = norm - sum_vals / pt.sqrt(n)