fix: remove references to deleted images from quotes

Controllers/UserContentController.cs

@@ -189,6 +189,18 @@ public class UserContentController : ControllerBase
         }
 
         // - from db
+        //    - first, from any quotes that reference it
+        List<Quote> quotesToModify = await _db.Quotes
+                                            .Include(q => q.Image)
+                                            .Where(q => q.Image == image)
+                                            .ToListAsync();
+
+        foreach (Quote quote in quotesToModify)
+        {
+            quote.Image = null;
+        }
+
+        //    - finally, from images table
         _db.Images.Remove(image);
         await _db.SaveChangesAsync();