Return Mono.error instead of runtime exception

Author: Milder Hernandez Cagua

agents/semantickernel-agents-core/src/main/java/com/microsoft/semantickernel/agents/chatcompletion/ChatCompletionAgent.java

@@ -157,7 +157,7 @@ private Mono<List<ChatMessageContent<?>>> internalInvokeAsync(
             );
 
         } catch (ServiceNotFoundException e) {
-            throw new RuntimeException(e);
+            return Mono.error(e);
         }
     }