New error in 3.6.7 - Unimplemented binary string operator

I found something than seems a bug upgrading from 3.6.6. To 3.6.7.

I have a piece with these traits:
Calculated property A: 10
Calculated property B: 0.5
Calculated property Res: A*B

I get this error in the error.log - Piece: Trait: Calculated Property - Res - Res Source: {AB} Error: Expression evaluation error. See the errorlog for more details.
Expression Audit:
Source type=Piece Trait
Source name=Piece:
Source description=Trait: Calculated Property - Res - Res
Source field=Expression
Source Expression={A
Error=internal Error: Unimplemented binary String operator

More info:
The same module was ok with Vassal 3.6.6.
If B is =1 or >1 there is no issue ( for ex. A=10, B=1.5, Res = 15.0).

Can someone help me?

Source expression {AB}, should not that be {A * B}?
We are also experiencing the leading 0 bug. 100*5/10 will work.

This is an unintended side effect of a change to allow leading zeros to be preserved. It is already fixed for 3.6.8 (that change now requires opting in); 3.6.8 should be released soon. If you need an immediate fix you can either revert to 3.6.6 or download a 3.6.8 snapshot (I forget exactly where to find them off the top of my head)…(edit:)or, use pald0n’s suggested change.

Edit: When pasting error logs, it’s best to put a line containing only three tic-marks (```) before and after the error log text, to avoid having the forum software read special characters (like *) as formatting codes.

If the 0.5 is a constant property or part of an expression, then using .5 instead should also work in 3.6.7