SparseArray: prevent unsafe array casting

Prevent e.g. np.array([1.0, np.nan]) cast to int resulting in some
large negative integer for np.nan.

Author: kernc

pandas/core/sparse/array.py

@@ -215,7 +215,8 @@ def __new__(cls, data, sparse_index=None, index=None, kind='integer',
             # array-like
             if sparse_index is None:
                 if dtype is not None:
-                    data = np.asarray(data, dtype=dtype)
+                    data = np.asarray(data)
+                    data = data.astype(dtype, casting='safe')
                 res = make_sparse(data, kind=kind, fill_value=fill_value)
                 values, sparse_index, fill_value = res
             else: