return tuple when broadcasting equations

src/equations/equations.jl

@@ -20,7 +20,7 @@ for the variables in `equations`. In particular, not the variables themselves ar
 """
 @inline eachvariable(equations::AbstractEquations) = Base.OneTo(nvariables(equations))
 
-Base.broadcastable(equations::AbstractEquations) = Ref(equations)
+Base.broadcastable(equations::AbstractEquations) = (equations,)
 
 @doc raw"""
     AbstractShallowWaterEquations{NDIMS, NVARS}