Fix bug from ticket scipy#1604 and add regression test.

Author: Keith Clawson

scipy/sparse/lil.py

@@ -195,7 +195,7 @@ def _get1(self, i, j):
         if pos != len(data) and row[pos] == j:
             return data[pos]
         else:
-            return 0
+            return self.dtype.type(0)
 
     def _slicetoseq(self, j, shape):
         if j.start is not None and j.start < 0:

scipy/sparse/tests/test_base.py

@@ -1609,6 +1609,11 @@ def test_inplace_ops(self):
 
             assert_array_equal(result.todense(), expected.todense())
 
+        # Ticket 1604. 
+        A = lil_matrix((1,3), dtype=np.dtype('float64'))
+        B = array([0.1,0.1,0.1])
+        A[0,:] += B
+        assert_array_equal(A[0,:].toarray().squeeze(), B)
 
     def test_lil_slice_assignment(self):
         B = lil_matrix((4,3))