Handle missing closer in Scriban section renderer

Added checks for the presence of the 'Closer' string before substring operations in ScribanDocumentSectionRenderer. This prevents exceptions when the closer is not found in the document content.

modules/docs/src/Volo.Docs.Domain.Shared/Volo/Docs/Documents/Rendering/ScribanDocumentSectionRenderer.cs

@@ -213,12 +213,15 @@ public class ScribanDocumentSectionRenderer : IDocumentSectionRenderer
                     documentContent.IndexOf(Opener, StringComparison.Ordinal) + Opener.Length
                 );
 
-                var betweenJsonOpenerAndCloser = afterJsonOpener.Substring(0,
-                    afterJsonOpener.IndexOf(Closer, StringComparison.Ordinal)
-                );
+                var closerIndex = afterJsonOpener.IndexOf(Closer, StringComparison.Ordinal);
+                if(closerIndex < 0)
+                {
+                    break;
+                }
+                var betweenJsonOpenerAndCloser = afterJsonOpener.Substring(0, closerIndex);
 
                 documentContent = afterJsonOpener.Substring(
-                    afterJsonOpener.IndexOf(Closer, StringComparison.Ordinal) + Closer.Length
+                    closerIndex + Closer.Length
                 );
 
                 if (!betweenJsonOpenerAndCloser.Contains(DocsTemplates))
@@ -257,9 +260,12 @@ public class ScribanDocumentSectionRenderer : IDocumentSectionRenderer
                     document.IndexOf(Opener, StringComparison.Ordinal) + Opener.Length
                 );
 
-                var betweenJsonOpenerAndCloser = afterJsonOpener.Substring(0,
-                    afterJsonOpener.IndexOf(Closer, StringComparison.Ordinal)
-                );
+                var closerIndex = afterJsonOpener.IndexOf(Closer, StringComparison.Ordinal);
+                if (closerIndex < 0)
+                {
+                    break;
+                }
+                var betweenJsonOpenerAndCloser = afterJsonOpener.Substring(0, closerIndex);
 
                 if (!betweenJsonOpenerAndCloser.Contains(DocsTemplates))
                 {