fix issue with NONE-ELEM on nil value

scripts/benchmarks.clj

@@ -165,7 +165,7 @@
 
 
 (let [data [1 2 3 4 5 6 7 8 9 10]]
-  (run-benchmark "first value of a vector" 10000000
+  (run-benchmark "first value of a size 10 vector" 10000000
     (first data)
     (select-any ALL data)
     (select-any FIRST data)

src/clj/com/rpl/specter.cljc

@@ -738,8 +738,10 @@
     (let [newe (next-fn NONE)]
       (if (identical? NONE newe)
         structure
-        (conj structure newe)
-        ))))
+        (if (nil? structure)
+          #{newe}
+          (conj structure newe)
+          )))))
 
 (defnav
   ^{:doc "Navigate to 'void' element before the sequence.

test/com/rpl/specter/core_test.cljc

@@ -1441,6 +1441,7 @@
   (is (predand= list? '(3 1 2) (setval s/BEFORE-ELEM 3 '(1 2))))
   (is (predand= list? '(1) (setval s/BEFORE-ELEM 1 nil)))
   (is (= #{1 2 3} (setval s/NONE-ELEM 3 #{1 2})))
+  (is (= #{1} (setval s/NONE-ELEM 1 nil)))
   )
 
 (deftest subvec-test