Fix (some) bugs

Author: penelopeysm

src/logdensityfunction.jl

@@ -135,7 +135,7 @@ function LogDensityProblems.logdensity_and_gradient(
     f::LogDensityFunction, θ::AbstractVector, adtype::ADTypes.AbstractADType
 )
     # Ensure we concretise the elements of the params.
-    θ = map(identity, getparams(f))
-    prep = DI.prepare_gradient(_flipped_logdensity, adtype, params, DI.Constant(f))
-    return DI.value_and_gradient(_flipped_logdensity, prep, adtype, params, DI.Constant(f))
+    # θ = map(identity, θ) # TODO: Is this needed?
+    prep = DI.prepare_gradient(_flipped_logdensity, adtype, θ, DI.Constant(f))
+    return DI.value_and_gradient(_flipped_logdensity, prep, adtype, θ, DI.Constant(f))
 end