Problem with Log Power FFT block

[Wojciech Kazubski]

Hello,
Some time ago I used  Log Power FFT block to detect a weak carrier in a noise. 
The output vector was passed through a Max block set to vector length  1024 to 
determine the highest value, which was the signal power. This worked fine in 
GR-3.7, but after upgrade to GR-3.8 (release 3.8.2) I get this error in Log 
Power FFT block:

Failed to eval ''part' if vlen == 1 else 'none'': name 'vlen' is not defined

Is this a bug or I am doing something wrong?

--
Wojciech Kazubski