Do not show message box to confirm uninstallation of old install when /VERYSILENT switch specified.

win32/tuxpaint.iss

@@ -255,6 +255,19 @@ begin
   Result := Path;
 end;
 
+function CmdLineParamExists(const Value: string): Boolean;
+var
+  I: Integer;
+begin
+  Result := False;
+  for I := 1 to ParamCount do
+    if CompareText(ParamStr(I), Value) = 0 then
+    begin
+      Result := True;
+      Exit;
+    end;
+end;
+
 Procedure ForceUninstallPreviousX86Install();
 var
   ResultCode: Integer;
@@ -262,6 +275,8 @@ begin
   if Is64BitInstallMode then
   begin
     if FileExists('C:\Program Files (x86)\TuxPaint\unins000.exe') then
+    begin
+      if CmdLineParamExists('/VERYSILENT') = False then
       begin
         if MsgBox('Old version will be uninstalled automatically.', mbInformation, MB_OKCANCEL) = IDOK then
         begin
@@ -270,6 +285,10 @@ begin
         else begin
           Abort;
         end;
+      end
+      else begin
+        Exec('C:\Program Files (x86)\TuxPaint\unins000.exe', '/VERYSILENT', '', SW_SHOW, ewWaitUntilTerminated, ResultCode);
+      end;
     end;
   end;
 end;