marktext: 0.16.0-rc.2 -> 0.16.1.

The upgrade apparently made it necessary to also add `XDG_DATA_DIRS`
to fix the crash mentioned in the added comment.

I copied this solution from:
`pkgs/applications/misc/devdocs-desktop/default.nix`

pkgs/applications/misc/marktext/default.nix

@@ -1,19 +1,25 @@
-{ appimageTools, fetchurl, lib }:
+{ appimageTools, fetchurl, lib, gsettings-desktop-schemas, gtk3 }:
 
 let
   pname = "marktext";
-  version = "v0.16.0-rc.2";
+  version = "v0.16.1";
 in
 appimageTools.wrapType2 rec {
   name = "${pname}-${version}-binary";
 
   src = fetchurl {
     url = "https://github.com/marktext/marktext/releases/download/${version}/marktext-x86_64.AppImage";
-    sha256 = "1w1mxa1j94zr36xhvlhzq8d77pi359vdxqb2j8mnz2bib9khxk9k";
+    sha256 = "1v2kjvccxfqj76c2krlmfnhrhs03y5n1pjcljgxaj2kc5vi80c1p";
   };
 
   profile = ''
     export LC_ALL=C.UTF-8
+  ''
+  # Fixes file open dialog error
+  #     GLib-GIO-ERROR **: 20:36:48.243: No GSettings schemas are installed on the system
+  # See https://github.com/NixOS/nixpkgs/pull/83701#issuecomment-608034097
+  + ''
+    export XDG_DATA_DIRS=${gsettings-desktop-schemas}/share/gsettings-schemas/${gsettings-desktop-schemas.name}:${gtk3}/share/gsettings-schemas/${gtk3.name}:$XDG_DATA_DIRS
   '';
 
   multiPkgs = null; # no 32bit needed