fix: null value for string is ""

src/renderer.zig

@@ -457,7 +457,7 @@ pub const Renderer = struct {
         _ = self;
         var w = buf.writer(alloc);
         switch (value) {
-            .null => try w.writeAll("null"),
+            .null => try w.writeAll(""),
             .bool => |b| try w.print("{}", .{b}),
             .int => |n| try w.print("{d}", .{n}),
             .float => |f| try w.print("{d}", .{f}),