fix the in-place hessvp

Author: mertkipcak

src/exp-kernel.jl

@@ -60,6 +60,6 @@ where the `expk` objective was last evaluated:
 """
 function hessvp!(expk::ExpKernel{T}, z::AbstractVector{T}) where T
     g = expk.g
-    z = g.*z
+    z .= g.*z
     return z
 end

src/logsumexp.jl

@@ -94,6 +94,6 @@ where the `lse` objective was last evaluated:
 """
 function hessvp!(lse::LogExpFunction{T}, z::AbstractVector{T}) where T
     g = lse.g
-    z = g.*(z .- (dot(g, z)))
+    z .= g.*(z .- (dot(g, z)))
     return z
 end