getty-zig: unitialized struct field that is not found in JSON gets freed causing segmentation fault

build.zig

const std = @import("std");

// Although this function looks imperative, note that its job is to
// declaratively construct a build graph that will be executed by an external
// runner.
pub fn build(b: *std.Build) void {
    // Standard target options allows the person running `zig build` to choose
    // what target to build for. Here we do not override the defaults, which
    // means any target is allowed, and the default is native. Other options
    // for restricting supported target set are available.
    const target = b.standardTargetOptions(.{});

    // Standard optimization options allow the person running `zig build` to select
    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
    // set a preferred release mode, allowing the user to decide how to optimize.
    const optimize = b.standardOptimizeOption(.{});

    const exe = b.addExecutable(.{
        .name = "bug",
        // In this case the main source file is merely a path, however, in more
        // complicated build scripts, this could be a generated file.
        .root_source_file = .{ .path = "src/main.zig" },
        .target = target,
        .optimize = optimize,
    });

    const opts = .{ .target = target, .optimize = optimize };
    const json_module = b.dependency("json", opts).module("json");
    exe.addModule("json", json_module);

    // This declares intent for the executable to be installed into the
    // standard location when the user invokes the "install" step (the default
    // step when running `zig build`).
    exe.install();

    // This *creates* a RunStep in the build graph, to be executed when another
    // step is evaluated that depends on it. The next line below will establish
    // such a dependency.
    const run_cmd = exe.run();

    // By making the run step depend on the install step, it will be run from the
    // installation directory rather than directly from within the cache directory.
    // This is not necessary, however, if the application depends on other installed
    // files, this ensures they will be present and in the expected location.
    run_cmd.step.dependOn(b.getInstallStep());

    // This allows the user to pass arguments to the application in the build
    // command itself, like this: `zig build run -- arg1 arg2 etc`
    if (b.args) |args| {
        run_cmd.addArgs(args);
    }

    // This creates a build step. It will be visible in the `zig build --help` menu,
    // and can be selected like this: `zig build run`
    // This will evaluate the `run` step rather than the default, which is "install".
    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);

    // Creates a step for unit testing.
    const exe_tests = b.addTest(.{
        .root_source_file = .{ .path = "src/main.zig" },
        .target = target,
        .optimize = optimize,
    });

    // Similar to creating the run step earlier, this exposes a `test` step to
    // the `zig build --help` menu, providing a way for the user to request
    // running the unit tests.
    const test_step = b.step("test", "Run unit tests");
    test_step.dependOn(&exe_tests.step);
}

build.zig.zon

.{
    .name = "app",
    .version = "1.0.0",
    .dependencies = .{
        .json = .{
            .url = "https://github.com/getty-zig/json/archive/7aee46311bfd1625f6641914c26a49e8d3085880.tar.gz",
            .hash = "12202fdb45919938ff856cc6129a52655415dabc4443dc9a05a16b74794d62fb57b7",
        },
    },
}

main.zig

const std = @import("std");
const json = @import("json");

const WorldState = struct {
    entities: std.ArrayList(Entity),

    pub fn deinit(self: *WorldState) void {
        self.entities.deinit();
    }
};

const Entity = struct {
    pub const @"getty.sb" = struct {
        pub const attributes = .{
            .Container = .{ .ignore_unknown_fields = true },
            ._cache = .{ .skip = true },
        };
    };
    pub const @"getty.db" = struct {
        pub const attributes = .{
            .Container = .{ .ignore_unknown_fields = true },
            ._cache = .{ .skip = true },
        };
    };

    id: u32 = 0,
    _cache: bool,
};

pub fn main() !void {
    var gpa: std.heap.GeneralPurposeAllocator(.{}) = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();

    const json_text =
        \\{
        \\  
        \\  "entities": [
        \\     { "id": 32 }
        \\  ]
        \\}
    ;
    const world = try json.fromSlice(gpa.allocator(), *WorldState, json_text);
    std.log.debug("entity count: {d}", .{world.entities.items.len});
    world.deinit();
    gpa.allocator().destroy(world);
}

main.zig (with a workaround _cache=undefined)

const std = @import("std");
const json = @import("json");

const WorldState = struct {
    entities: std.ArrayList(Entity),

    pub fn deinit(self: *WorldState) void {
        self.entities.deinit();
    }
};

const Entity = struct {
    pub const @"getty.sb" = struct {
        pub const attributes = .{
            .Container = .{ .ignore_unknown_fields = true },
            ._cache = .{ .skip = true },
        };
    };
    pub const @"getty.db" = struct {
        pub const attributes = .{
            .Container = .{ .ignore_unknown_fields = true },
            ._cache = .{ .skip = true },
        };
    };

    id: u32 = 0,
    _cache: bool = undefined,
};

pub fn main() !void {
    var gpa: std.heap.GeneralPurposeAllocator(.{}) = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();

    const json_text =
        \\{
        \\  
        \\  "entities": [
        \\     { "id": 32 }
        \\  ]
        \\}
    ;
    const world = try json.fromSlice(gpa.allocator(), *WorldState, json_text);
    std.log.debug("entity count: {d}", .{world.entities.items.len});
    world.deinit();
    gpa.allocator().destroy(world);
}