Crash after clicking "Schedule a message" button.

[YYYSSSHHH]

Environment Info：
App Version: 0.5 (5)
Android simulator version: 6.0.1

Repro Steps：
1.All permissions of the app are granted.
2.Click the "Schedule a message" button, then the app will crash.

Runtime Log：
Process: com.github.yeriomin.smsscheduler, PID: 2848
java.lang.RuntimeException: Unable to resume activity {com.github.yeriomin.smsscheduler/com.github.yeriomin.smsscheduler.activity.AddSmsActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.List.get(int)' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3138)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3169)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2508)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1353)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5539)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:745)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:635)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:107)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.List.get(int)' on a null object reference
at com.github.yeriomin.smsscheduler.view.BuilderSimCard.build(BuilderSimCard.java:35)
at com.github.yeriomin.smsscheduler.view.BuilderSimCard.build(BuilderSimCard.java:18)
at com.github.yeriomin.smsscheduler.activity.AddSmsActivity.buildForm(AddSmsActivity.java:89)
at com.github.yeriomin.smsscheduler.activity.AddSmsActivity.onResume(AddSmsActivity.java:75)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1258)
at android.app.Activity.performResume(Activity.java:6355)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3121)
... 11 more

Do you judge this as a defect? Thank you for your reply！