Encoding of query params doesn't work when marked optional

[maorelias]

When marked as optional:

(def compiled
  (contextual.http/compile-request '{:query-params {:timestamp ^:optional timestamp}, :method "get"} 
  {'timestamp (contextual.core/path :ts)} 
  {} 
  {:serialize-query-params true}))

(contextual.core/invoke compiled {:ts "2021-05-28 16:22:55.000+00   00"})
=> {:method "get", :url "?timestamp=2021-05-28 16:22:55.000+00   00"}

When not marked as optional:

(def compiled
  (contextual.http/compile-request '{:query-params {:timestamp timestamp}, :method "get"} 
  {'timestamp (contextual.core/path :ts)} 
  {} 
  {:serialize-query-params true}))

(contextual.core/invoke compiled {:ts "2021-05-28 16:22:55.000+00   00"})
=> {:method "get", :url "?timestamp=2021-05-28%2016%3A22%3A55.000%2B00%20%20%2000"}