[mono][debugger] Protecting against changing the protocol version (#122102)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: thaystg

src/mono/mono/component/debugger-agent.c

@@ -7185,6 +7185,10 @@ vm_commands (int command, int id, guint8 *p, guint8 *end, Buffer *buf)
 		break;
 	}
 	case CMD_VM_SET_PROTOCOL_VERSION: {
+		if (protocol_version_set) {
+			PRINT_DEBUG_MSG (1, "[dbg] Trying to reset the protocol version, ignoring it\n");
+			break;
+		}
 		major_version = decode_int (p, &p, end);
 		minor_version = decode_int (p, &p, end);
 		if (p < end)