!116 【轻量级 PR】：update docs-en/readme/distributed-communication-subsystem.md.

Merge pull request !116 from robinyin/N/A

docs-en/readme/distributed-communication-subsystem.md

@@ -131,7 +131,7 @@ int OnSessionOpenedEventTest(int sessionId)
 // Register the service session service and its callbacks with the soft bus.
 int StartSessionServer()
 {
-    if (g_sessionCallback != NULL) {
+    if (g_sessionCallback == NULL) {
         g_sessionCallback = (struct ISessionListener*)malloc(sizeof(struct ISessionListener));
     }
     if (g_sessionCallback == NULL) {