fix(installed): Use 'System.Nullable<bool>' for param 'global' (#5088)

Author: niheaven

CHANGELOG.md

@@ -11,6 +11,7 @@
 ### Bug Fixes
 
 - **core:** Avoid deadlock in `Invoke-ExternalCommand` ([#5064](https://github.com/ScoopInstaller/Scoop/issues/5064))
+- **core:** Use 'System.Nullable<bool>' for param 'global' ([#5088](https://github.com/ScoopInstaller/Scoop/issues/5088))
 - **install:** Move from cache when `--no-cache` is specified ([#5039](https://github.com/ScoopInstaller/Scoop/issues/5039))
 - **scoop-status:** Correct formatting of `Info` output ([#5047](https://github.com/ScoopInstaller/Scoop/issues/5047))
 

lib/core.ps1

@@ -225,8 +225,8 @@ function cache_path($app, $version, $url) { "$cachedir\$app#$version#$($url -rep
 
 # apps
 function sanitary_path($path) { return [regex]::replace($path, "[/\\?:*<>|]", "") }
-function installed($app, $global) {
-    if (-not $PSBoundParameters.ContainsKey('global')) {
+function installed($app, [Nullable[bool]]$global) {
+    if ($null -eq $global) {
         return (installed $app $false) -or (installed $app $true)
     }
     # Dependencies of the format "bucket/dependency" install in a directory of form