Cherry-pick: Add null check for Wi-Fi command

When WifiService is not ready during boot phase and Wi-Fi command
is executed on console, NullPointerException happens.
To prevent this, null check is needed.

Test: Manual test
Bug: 64040515
Change-Id: I5684cdc7661b7d93fd6f2ac61863919077d12935
Merged-In: I5684cdc7661b7d93fd6f2ac61863919077d12935

cmds/svc/src/com/android/commands/svc/WifiCommand.java

@@ -51,6 +51,10 @@ public class WifiCommand extends Svc.Command {
             if (validCommand) {
                 IWifiManager wifiMgr
                         = IWifiManager.Stub.asInterface(ServiceManager.getService(Context.WIFI_SERVICE));
+                if (wifiMgr == null) {
+                    System.err.println("Wi-Fi service is not ready");
+                    return;
+                }
                 try {
                     wifiMgr.setWifiEnabled("com.android.shell", flag);
                 }