Yet another where helper fix

Support nil conditions

src/honey/sql/helpers.cljc

@@ -10,14 +10,19 @@
 
 (defn- and-merge
   [current args]
+  (let [args (remove nil? args)]
     (cond (= :and (first current))
           (default-merge current args)
           (seq current)
+          (if (seq args)
             (default-merge [:and current] args)
+            current)
           (= 1 (count args))
           (vec (first args))
+          (seq args)
+          (default-merge [:and] args)
           :else
-        (default-merge [:and] args)))
+          (vec current))))
 
 (def ^:private special-merges
   {:where  #'and-merge