Fixes query_one? handling no rows (#86)

spec/dummy_driver_spec.cr

@@ -190,6 +190,13 @@ describe DummyDriver do
         end
       end
 
+      it "with as, no rows" do
+        with_dummy do |db|
+          value = db.query_one?("", as: {a: Int64, b: Int64})
+          value.should be_nil
+        end
+      end
+
       it "with as, just one" do
         with_dummy do |db|
           value = db.query_one?("3", as: Int64)

src/db/query_methods.cr

@@ -169,7 +169,7 @@ module DB
     # typeof(result) # => NamedTuple(age: String, name: Int32) | Nil
     # ```
     def query_one?(query, *args, as types : NamedTuple)
-      query_one(query, *args) do |rs|
+      query_one?(query, *args) do |rs|
         rs.read(**types)
       end
     end