android studio logcat does not show the reason of crashes when i run my app on a real phone

I have a strange problem. when I run my app on Genymotion with android 4.1, everything is good and Logcat works fine and shows everything. but when I run the same app on a real phone(Huawei honour 7 with Android 6), and my app gets crash, logCat does not show the reason for that crash. in the other word, log cat does not show Exceptions. can anyonehelp me?thanks

maybe be useful:

logCat After a crash:

build.gradle(module app)

apply plugin: 'com.android.application'android {    compileSdkVersion 26    defaultConfig {        applicationId "my.application.id"        minSdkVersion 15        targetSdkVersion 26        versionCode 1        versionName "1.0"        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"    }    buildTypes {        release {            minifyEnabled false            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'        }    }}dependencies {    ....}