fix: handle requests with a non-integer list for category_id

Controllers/QuoteController.cs

@@ -54,10 +54,21 @@ public class QuotesController : ControllerBase
         var totalQuotes = await _db.Quotes.CountAsync();
         const int PageSize = 10;
 
-        List<int>? categories = category_id?
-                                    .Split(",")
-                                    .Select(Int32.Parse)
-                                    .ToList();
+        List<int>? categories;
+        try
+        {
+            categories = category_id?
+                                .Split(",")
+                                .Select(Int32.Parse)
+                                .ToList();
+        } catch
+        {
+            // Try to catch badly formatted requests
+            return BadRequest(new ErrorDTO {
+                Status = "error",
+                Error_msg = "Category_id can be either an integer, or comma separated integers"
+            });
+        }
 
         if (page_no <= 0)
         {