Bug in redcal solver

[steven-murray]

There is an error that comes up in the test_redcal_run test sometimes:

     def get_weighted_data(self):
        '''Return y = data * wgt**.5 as a 2D vector, regardless of original data/wgt shape.'''
        dtype = self.dtype # default
        if self.re_im_split:
            if dtype == np.float32:
                dtype = np.complex64
            else:
                dtype = np.complex128
        d = np.array([self.data[k] for k in self.keys], dtype=dtype)
        if len(self.wgts) > 0:
            w = np.array([self.wgts[k] for k in self.keys])
            w.shape += (1,) * (d.ndim-w.ndim)
            d.shape += (1,) * (w.ndim-d.ndim)
            d = d*(w**.5)
            # this is w**.5 because A already has a factor of w**.5 in it, so
            # (At N^-1 A)^1 At N^1 y ==> (At A)^1 At d (where d is the result of this
            # function and A is redefined to include half of the weights)
        self._data_shape = d.shape[1:] # store for reshaping sols to original
>       d.shape = (d.shape[0],-1) # Flatten
E       ValueError: cannot reshape array of size 0 into shape (0,newaxis)