CF(0) * TestFunction does not have TestFunction

[CAarset]

Ran into an unexpected issue applying a PDE solve to a coefficient-function-based source: The code

v = fes.TestFunction()
LinearForm(f * v * dx)

works for any CoefficientFunction f except f = CoefficientFunction(0), in which case it fails with error "Linearform must have TestFunction". The reason is apparent from

print(CoefficientFunction(0) * VV)

returning ZeroCoefficientFunction, while

print(CoefficientFunction(1) * VV)

returns

coef binary operation '*', real
coef unary operation ' ', real
coef 1, real
coef test-function diffop = Id, real

While this makes some sense from a compression perspective (0 times anything is 0), it makes applying PDE solves to a CF prone to unexpected failure, and notionally it also removes the obvious way to define a 0-LinearForm. Note that interpolating CoefficientFunction(0) to a GridFunction on the fes does work and createas a 0-LinearForm as expected, but is a step I'd rather bypass.

Minimal non-working example attached.
CF0.txt

[Horep]

As a workaround, you can wrap your float with Parameter.
This prevents the error from occurring, i.e. write
f0 = CoefficientFunction(Parameter(0)).
The other way to produce a 0-LinearForm
is to write
LinearForm(fes)
which will assemble to a vector of zeroes.