Use a lightweight timer to delay task

This should also fix CID18182

src/Forms/VobSubOcr.cs

@@ -14,6 +14,7 @@ using System.IO;
 using System.Reflection;
 using System.Text;
 using System.Text.RegularExpressions;
+using System.Threading.Tasks;
 using System.Windows.Forms;
 using System.Xml;
 
@@ -7351,17 +7352,11 @@ namespace Nikse.SubtitleEdit.Forms
             {
                 var last = _lastAdditions[_lastAdditions.Count - 1];
                 numericUpDownStartNumber.Value = last.Index + 1;
-                Timer t = new Timer();
-                t.Interval = 200;
-                t.Tick += t_Tick;
-                t.Start();
-            }
-        }
 
-        private void t_Tick(object sender, EventArgs e)
-        {
-            (sender as Timer).Stop();
-            ButtonStartOcrClick(null, null);
+                // Simulate a click on ButtonStartOcr in 200ms.
+                var uiContext = TaskScheduler.FromCurrentSynchronizationContext();
+                Utilities.TaskDelay(200).ContinueWith(_ => ButtonStartOcrClick(null, null), uiContext);
+            }
         }
 
         private void VobSubOcr_Resize(object sender, EventArgs e)

src/Logic/Utilities.cs

@@ -12,6 +12,7 @@ using System.Net;
 using System.Reflection;
 using System.Text;
 using System.Text.RegularExpressions;
+using System.Threading.Tasks;
 using System.Windows.Forms;
 using System.Xml;
 
@@ -4115,5 +4116,17 @@ namespace Nikse.SubtitleEdit.Logic
             return text;
         }
 
+        /// <summary>
+        /// Creates a task that will complete after a time delay.
+        /// </summary>
+        /// <param name="millisecondsDelay">The number of milliseconds to wait before completing the returned task.</param>
+        /// <returns>A task that represents the time delay.</returns>
+        public static Task TaskDelay(int millisecondsDelay)
+        {
+            var tcs = new TaskCompletionSource<object>();
+            var t = new System.Threading.Timer(_ => tcs.SetResult(null));
+            t.Change(millisecondsDelay, -1);
+            return tcs.Task;
+        }
     }
 }