Composer crashes when an invalid mail address is about to be shown in recipient selector

[morckx]

Steps to reproduce

1. create a contact with a name and an invalid mail address, e. g. "(none)"
2. click '+' to compose new message
3. type first letters of the contact name until it should be shown

Logcat

09-09 22:12:26.740 10531 10531 E AndroidRuntime: FATAL EXCEPTION: main
09-09 22:12:26.740 10531 10531 E AndroidRuntime: Process: com.fsck.k9, PID: 10531
09-09 22:12:26.740 10531 10531 E AndroidRuntime: Theme: themes:{default=overlay:com.brit.swiftdark, fontPkg:com.brit.swiftdark, com.android.systemui=overlay:com.brit.s
wiftdark, com.android.systemui.navbar=overlay:com.brit.swiftdark}
09-09 22:12:26.740 10531 10531 E AndroidRuntime: java.lang.NullPointerException: Attempt to invoke interface method 'int java.lang.CharSequence.length()' on a null obj
ect reference
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.text.SpannableString.<init>(SpannableString.java:30)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.text.Spannable$Factory.newSpannable(Spannable.java:67)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at com.fsck.k9.activity.compose.RecipientAdapter.highlightText(RecipientAdapter.java:182)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at com.fsck.k9.activity.compose.RecipientAdapter.bindView(RecipientAdapter.java:92)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at com.fsck.k9.activity.compose.RecipientAdapter.getView(RecipientAdapter.java:72)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.AbsListView.obtainView(AbsListView.java:2346)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.ListPopupWindow$DropDownListView.obtainView(ListPopupWindow.java:1734)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.ListView.measureHeightOfChildren(ListView.java:1281)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.ListPopupWindow.buildDropDown(ListPopupWindow.java:1209)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.ListPopupWindow.show(ListPopupWindow.java:584)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.AutoCompleteTextView.showDropDown(AutoCompleteTextView.java:1106)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at com.fsck.k9.view.RecipientSelectView.showDropDown(RecipientSelectView.java:226)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.AutoCompleteTextView.updateDropDownForFilter(AutoCompleteTextView.java:975)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.AutoCompleteTextView.-wrap2(AutoCompleteTextView.java)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.widget.AutoCompleteTextView$PopupDataSetObserver$1.run(AutoCompleteTextView.java:1300)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.os.Handler.handleCallback(Handler.java:739)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.os.Handler.dispatchMessage(Handler.java:95)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.os.Looper.loop(Looper.java:148)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at android.app.ActivityThread.main(ActivityThread.java:5463)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at java.lang.reflect.Method.invoke(Native Method)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
09-09 22:12:26.740 10531 10531 E AndroidRuntime:        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
09-09 22:12:26.741  1716  4127 W ActivityManager:   Force finishing activity com.fsck.k9/.activity.MessageCompose

Environment

K-9 Mail version: 5.111 (master)

Android version:
6.0.1