Refactor code for readability in KaraokeEffect.cs

Expanded conditional statements' blocks in KaraokeEffect.cs to improve readability and maintainability. This change does not alter the overall functionality of the code but makes it easier to handle and debug.

src/libse/Common/TextEffect/KaraokeEffect.cs

@@ -47,9 +47,15 @@ namespace Nikse.SubtitleEdit.Core.Common.TextEffect
                 if (HtmlUtil.IsStartTagSymbol(ch))
                 {
                     var closeIdx = text.IndexOf(HtmlUtil.GetClosingPair(ch), i + 1);
-                    if (closeIdx < 0) return i;
+                    if (closeIdx < 0)
+                    {
+                        return i;
+                    }
+                }
+                else
+                {
+                    return i;
                 }
-                else return i;
             }
 
             return 0;