Avoid flickering the main window when wsl is not installed.

Checking whether wsl installed is in the main window, so the window
must be created and shown anyway even if wsl is missing.
This patch moves the checking right in the application initialization
before the window will be created.

src/mainwindow.pas

@@ -46,7 +46,6 @@   TWslGuiToolMainWindow = class(TForm)
     IconListToolbar: TImageList;
     ToolBar1: TToolBar;
     ToolButtonRun: TToolButton;
-    procedure CheckIfWslIsInstalledExecute(Sender: TObject);
     procedure FormCreate(Sender: TObject);
     procedure FormDestroy(Sender: TObject);
     procedure FormHide(Sender: TObject);
@@ -235,18 +234,6 @@ function NumberItemSelected(List: TListView): integer;
   end;
 end;
 
-procedure TWslGuiToolMainWindow.CheckIfWslIsInstalledExecute(Sender: TObject);
-begin
-  if not WslCommandLine.IsWslInstalled()
-  then begin
-    Application.MessageBox(
-      'WSL seems to be not installed!',
-      'Error',
-      MB_OK + MB_ICONERROR);
-    Application.Terminate;
-  end;
-end;
-
 procedure TWslGuiToolMainWindow.FormCreate(Sender: TObject);
 begin
   BackgroundProcessProgressBar := TBackgroundProcessProgressBar.Create(Self);
@@ -258,7 +245,6 @@ procedure TWslGuiToolMainWindow.FormCreate(Sender: TObject);
 
   StatusbarImageIndex := -1;
   StatusbarMessage := '';
-  Self.CheckIfWslIsInstalledExecute(Sender);
 end;
 
 procedure TWslGuiToolMainWindow.FormDestroy(Sender: TObject);

src/wslguitool.lpr

@@ -7,17 +7,30 @@
   cthreads,
   {$ENDIF}{$ENDIF}
   Interfaces, // this includes the LCL widgetset
-  Forms, MainWindow, WslApi, WslCommandLine, WslRegistry, ApplicationInfo,
+  Forms, LCLType, MainWindow, WslApi, WslCommandLine, WslRegistry, ApplicationInfo,
   AboutWindow, DistributionPropertiesWindow, ImportDistributionWindow,
   RunCommandWithUserWindow, PromptWindow, BackgroundProcessProgressBar, ProcessResultDisplay;
 
 {$R *.res}
 
 begin
   RequireDerivedFormResource:=True;
+
   Application.Scaled:=True;
   Application.Initialize;
-  Application.CreateForm(TWslGuiToolMainWindow, WslGuiToolMainWindow);
-  Application.Run;
+
+  if WslCommandLine.IsWslInstalled() then
+  begin
+    Application.CreateForm(TWslGuiToolMainWindow, WslGuiToolMainWindow);
+    Application.Run;
+  end
+  else begin
+    Application.MessageBox(
+      'WSL seems to be not installed!',
+      'Error',
+      MB_OK + MB_ICONERROR
+    );
+    Application.Terminate;
+  end;
 end.