FRAP agent bug

[zhangm269]

Describe the bug
frap agent file has a bug

To Reproduce
Steps to reproduce the behavior:

1. Go to 'agent' folder
2. Click on 'frap'
3. Scroll down to Line 440
4. See “demand = states[:, i:i+self.demand_shape]”

Expected behavior
The expression i: i+demandshape in this code is incorrect when the demandshape is not 1.
it should be written as demand = states[:, i * self.demand_shape:(i + 1) * self.demand_shape]

[wingsweihua]

@ShawLen Please take a look