fix: C null values causing panic if prompt or path input is canceled

src/bindings.zig

@@ -4,12 +4,13 @@ pub const osdialog_color = extern struct { r: u8, g: u8, b: u8, a: u8 };
 pub const osdialog_filters = extern struct {};
 
 pub extern fn osdialog_message(level: c_int, buttons: c_int, message: [*c]const u8) c_int;
-pub extern fn osdialog_prompt(level: c_int, message: [*c]const u8, text: [*c]const u8) [*c]u8;
+pub extern fn osdialog_prompt(level: c_int, message: [*c]const u8, text: [*c]const u8) ?*anyopaque;
 pub extern fn osdialog_color_picker(color: *osdialog_color, opacity: c_int) c_int;
-pub extern fn osdialog_file(action: c_int, path: [*c]const u8, filename: [*c]const u8, filters: ?*osdialog_filters) [*c]u8;
+pub extern fn osdialog_file(action: c_int, path: [*c]const u8, filename: [*c]const u8, filters: ?*osdialog_filters) ?*anyopaque;
 
-pub fn toZString(allocator: std.mem.Allocator, c_str_opt: ?[*c]u8) ?[:0]u8 {
-	const c_string = c_str_opt orelse return null;
+pub fn toZString(allocator: std.mem.Allocator, c_str_opt: ?*anyopaque) ?[:0]u8 {
+	const ptr = c_str_opt orelse return null;
+	const c_string: [*c]u8 = @ptrCast(ptr);
 	defer std.c.free(c_string);
 	const z_string: [:0]u8 = std.mem.span(c_string);
 	return allocator.dupeZ(u8, z_string) catch return null;