NullPointerException org.chromium.android_webview.AwContents$AwViewMethodsImpl.onDragEvent

问题

about 10 days ago, my app started to record this exception (seen on dev console):

java.lang.NullPointerException: 
  at org.chromium.android_webview.AwContents$AwViewMethodsImpl.onDragEvent (AwContents.java:191)
  at com.android.webview.chromium.WebViewChromium.onDragEvent (WebViewChromium.java:782)
  at android.webkit.WebView.onDragEvent (WebView.java:2554)
  at android.view.View.dispatchDragEvent (View.java:22202)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1431)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewRootImpl.handleDragEvent (ViewRootImpl.java:6308)
  at android.view.ViewRootImpl.-wrap11 (ViewRootImpl.java)
  at android.view.ViewRootImpl$ViewRootHandler.handleMessage (ViewRootImpl.java:4199)
  at android.os.Handler.dispatchMessage (Handler.java:102)
  at android.os.Looper.loop (Looper.java:154)
  at android.app.ActivityThread.main (ActivityThread.java:6776)
  at java.lang.reflect.Method.invoke (Native Method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:1496)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1386)

I've no idea it could be (so i can't replicate it) and stacktrace covers none of my classes. About this exception I only know that:

effects only devices with android 7 or 7.1
first time occurred 11 Oct 2017
it occurred about 50 times per days, until 5 Nov 2017
it exploded from 6 Nov 2017 until now with about 340 occurrences per day

Users-app-usage is stable from about 1 year (3000 sessions per days, 15minutes per sessions). App is a solitaire card games (no framework as libgdx used).

This is my build.gradle:

apply plugin: 'com.android.application'

android {
    useLibrary 'org.apache.http.legacy'
    compileSdkVersion 25
    buildToolsVersion '25.0.3'
    defaultConfig {
        applicationId "com.pisano.app.solitari"
        minSdkVersion 15
        targetSdkVersion 23

        multiDexEnabled = true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
        debug {
            signingConfig signingConfigs.config
        }
    }

    dexOptions {
        javaMaxHeapSize "4g"
    }
}

dependencies {
    compile 'com.nostra13.universalimageloader:universal-image-loader:1.9.5'
    compile project(':pagecontrol')
    compile 'com.facebook.android:facebook-android-sdk:4.26.0'
    compile 'com.google.android.gms:play-services-games:11.2.2'
    compile 'com.google.android.gms:play-services-plus:11.2.2'
    compile 'com.google.android.gms:play-services-analytics:11.2.2'
    compile 'com.google.android.gms:play-services-location:11.2.2'
    compile 'com.google.firebase:firebase-core:11.2.2'
    compile 'com.google.firebase:firebase-ads:11.2.2'

}

apply plugin: 'com.google.gms.google-services'

Thank you very much.