modern7z: Fix uninstaller logic

Author: SorYoshino

bucket/modern7z.json

@@ -34,9 +34,11 @@
     "uninstaller": {
         "script": [
             "$7z_path = friendly_path -Path $(Get-CommandPath -Command '7z.exe')",
-            "$codecs_dir = Join-Path -Path $(Split-Path -Path $7z_path -Parent) -ChildPath 'Codecs'",
-            "Get-ChildItem -Path $dir -Exclude '*.json', 'ReadMe.txt' | ForEach-Object {",
-            "    Remove-Item -Path \"$codecs_dir\\$($_.Name)\" -Recurse -Force -ErrorAction SilentlyContinue",
+            "if ($null -ne $7z_path) {",
+            "    $codecs_dir = Join-Path -Path $(Split-Path -Path $7z_path -Parent) -ChildPath 'Codecs'",
+            "    Get-ChildItem -Path $dir -Exclude '*.json', 'ReadMe.txt' | ForEach-Object -Process {",
+            "        Remove-Item -Path \"$codecs_dir\\$($_.Name)\" -Recurse -Force -ErrorAction SilentlyContinue",
+            "    }",
             "}"
         ]
     },