Fix :run!.

Broken by me in 4582cb2b148c.

--HG--
extra : rebase_source : 57fb60a9e103c70b810a3140f46da4b45f552f7a

common/modules/io.jsm

@@ -841,7 +841,7 @@ unlet s:cpo_save
 
                 modules.autocommands.trigger("ShellCmdPost", {});
             }, {
-                argCount: "1",
+                argCount: "?",
                 bang: true,
                 // This is abominably slow.
                 // completer: function (context) completion.shellCommand(context),

common/tests/functional/testCommands.js

@@ -45,7 +45,6 @@ function toolbarState(selector, state)
 
 var tests = {
     "!": {
-        error: [""],
         multiOutput: ["echo foo"]
     },
     get Clistkeys() this.listcommands,