firefox: Set default (empty) extra extensions

Change-Id: I7f557448456202fe8af056af0dfd682c8f5e1bb6
Reviewed-on: https://git.clicks.codes/c/Chimera/NixFiles/+/653
Reviewed-by: Samuel Shuert <coded@clicks.codes>
Tested-by: Samuel Shuert <coded@clicks.codes>
diff --git a/modules/home/browser/firefox/default.nix b/modules/home/browser/firefox/default.nix
index 3fcbf06..2bc37ee 100644
--- a/modules/home/browser/firefox/default.nix
+++ b/modules/home/browser/firefox/default.nix
@@ -16,6 +16,7 @@
     extraExtensions = lib.mkOption {
       type = lib.types.listOf lib.types.package;
       description = "Extra extensions to add to firefox";
+      default = [ ];
     };
   };
   config = lib.mkIf config.chimera.browser.firefox.enable ({