Handle missing file attachments in message processing

app/MindWork AI Studio/Chat/ContentText.cs

@@ -155,6 +155,18 @@ public sealed class ContentText : IContent
         sb.AppendLine(this.Text);
 
         if(this.FileAttachments.Count > 0)
+        {
+            // Filter out files that no longer exist
+            var existingFiles = this.FileAttachments.Where(File.Exists).ToList();
+
+            // Log warning for missing files
+            var missingFiles = this.FileAttachments.Except(existingFiles).ToList();
+            if (missingFiles.Count > 0)
+                foreach (var missingFile in missingFiles)
+                    LOGGER.LogWarning("File attachment no longer exists and will be skipped: '{MissingFile}'", missingFile);
+
+            // Only proceed if there are existing files
+            if (existingFiles.Count > 0)
             {
                 // Check Pandoc availability once before processing file attachments
                 var pandocState = await Pandoc.CheckAvailabilityAsync(Program.RUST_SERVICE, showMessages: true, showSuccessMessage: false);
@@ -167,7 +179,7 @@ public sealed class ContentText : IContent
                 {
                     sb.AppendLine();
                     sb.AppendLine("The following files are attached to this message:");
-                foreach(var file in this.FileAttachments)
+                    foreach(var file in existingFiles)
                     {
                         sb.AppendLine();
                         sb.AppendLine("---------------------------------------");
@@ -179,6 +191,8 @@ public sealed class ContentText : IContent
                     }
                 }
             }
+        }
+        
         return sb.ToString();
     }