java.lang.NullPointerException: java.lang.String com.hyphenate.chat.EMCallSession.getExt()

java.lang.RuntimeException: Unable to resume activity {com.yunjiang.convenient/com.yunjiang.convenient.activity.VideoCallActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.hyphenate.chat.EMCallSession.getExt()' on a null object reference at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3229) at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3307) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1484) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.hyphenate.chat.EMCallSession.getExt()' on a null object reference at com.yunjiang.convenient.activity.VideoCallActivity.onResume(VideoCallActivity.java) at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1259) at android.app.Activity.performResume(Activity.java:6400) at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3218) ... 8 more java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.hyphenate.chat.EMCallSession.getExt()' on a null object reference at com.yunjiang.convenient.activity.VideoCallActivity.onResume(VideoCallActivity.java) at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1259) at android.app.Activity.performResume(Activity.java:6400) at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3218) at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3307) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1484) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
 实在视频通话的时候获取扩展消息出现的问题