Process: com.procurenetworks.inventoryapp, PID: 28639
com.facebook.react.common.JavascriptException: undefined is not an object (evaluating 'i.default.Crashlytics'), stack:
@689:1574
d@2:768
n@2:409
t@2:262
@530:310
d@2:768
n@2:409
t@2:262
@385:161
d@2:768
n@2:409
t@2:262
@305:191
d@2:768
n@2:409
t@2:262
@12:42
d@2:768
n@2:339
t@2:262
global code@879:8

    at com.facebook.react.modules.core.ExceptionsManagerModule.showOrThrowError(ExceptionsManagerModule.java:54)
    at com.facebook.react.modules.core.ExceptionsManagerModule.reportFatalException(ExceptionsManagerModule.java:38)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.facebook.react.bridge.JavaMethodWrapper.invoke(JavaMethodWrapper.java:372)
    at com.facebook.react.bridge.JavaModuleWrapper.invoke(JavaModuleWrapper.java:160)
    at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method)
    at android.os.Handler.handleCallback(Handler.java:873)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:29)
    at android.os.Looper.loop(Looper.java:193)
    at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:192)
    at java.lang.Thread.run(Thread.java:764)

I am getting following error while working with fabrics, i have gone through all the steps in readme.md i followed all steps but don't know why i am getting error.

here are my configuration file:
in ** manifest ** file :

Main Application.java

import android.app.Application;
import com.crashlytics.android.Crashlytics;
import com.facebook.react.BuildConfig;
import com.facebook.react.ReactApplication;
import com.facebook.react.ReactNativeHost;
import com.facebook.react.ReactPackage;
import com.facebook.react.shell.MainReactPackage;
import com.facebook.soloader.SoLoader;
import com.smixx.fabric.FabricPackage;

import java.util.Arrays;
import java.util.List;

import io.fabric.sdk.android.Fabric;

public class MainApplication extends Application implements ReactApplication {

private final ReactNativeHost mReactNativeHost = new ReactNativeHost(this) {
@OverRide
public boolean getUseDeveloperSupport() {
return BuildConfig.DEBUG;
}

@Override
protected List<ReactPackage> getPackages() {
  return Arrays.<ReactPackage>asList(
        new MainReactPackage(),
        new FabricPackage()
  );
}

@Override
protected String getJSMainModuleName() {
  return "index";
}

};

@OverRide
public ReactNativeHost getReactNativeHost() {
return mReactNativeHost;
}

@OverRide
public void onCreate() {
super.onCreate();
SoLoader.init(this, /* native exopackage */ false);
Fabric.with(this, new Crashlytics());
}

}

app/build.gradle
apply plugin: "com.android.application"

buildscript {
repositories {
maven { url 'https://maven.fabric.io/public' }
}
dependencies {
classpath 'io.fabric.tools:gradle:1.+'
}
}
apply plugin: 'io.fabric'
repositories {
maven { url 'https://maven.fabric.io/public' }
}

import com.android.build.OutputFile
project.ext.react = [
entryFile: "index.js"
]

apply from: "../../node_modules/react-native/react.gradle"

def enableSeparateBuildPerCPUArchitecture = false

def enableProguardInReleaseBuilds = false

android {
compileSdkVersion 26
buildToolsVersion "26.0.1"

defaultConfig {
    applicationId "******"
    minSdkVersion 16
    targetSdkVersion 26
    versionCode 19
    versionName "4.7"
    ndk {
        abiFilters "armeabi-v7a", "x86"
    }
    multiDexEnabled true
}
 signingConfigs {
    release {
        if (project.hasProperty('MYAPP_RELEASE_STORE_FILE')) {
            storeFile file(MYAPP_RELEASE_STORE_FILE)
            storePassword MYAPP_RELEASE_STORE_PASSWORD
            keyAlias MYAPP_RELEASE_KEY_ALIAS
            keyPassword MYAPP_RELEASE_KEY_PASSWORD
        }
    }
}
splits {
    abi {
        reset()
        enable enableSeparateBuildPerCPUArchitecture
        universalApk false  // If true, also generate a universal APK
        include "armeabi-v7a", "x86"
    }
}
buildTypes {
    release {
        signingConfig signingConfigs.release
        minifyEnabled enableProguardInReleaseBuilds
        proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
    }
}
// applicationVariants are e.g. debug, release
applicationVariants.all { variant ->
    variant.outputs.each { output ->
        def versionCodes = ["armeabi-v7a":1, "x86":2]
        def abi = output.getFilter(OutputFile.ABI)
        if (abi != null) {  // null for the universal-debug, universal-release variants
            output.versionCodeOverride =
                    versionCodes.get(abi) * 1048576 + defaultConfig.versionCode
        }
    }
}

}

dependencies {
implementation project(':react-native-fabric')
}
implementation fileTree(dir: "libs", include: ["*.jar"])
implementation "com.android.support:appcompat-v7:23.0.1"
implementation "com.facebook.react:react-native:+" // From node_modules
implementation('com.crashlytics.sdk.android:crashlytics:2.9.3@aar') {
transitive = true
}

}
task copyDownloadableDepsToLibs(type: Copy) {
from configurations.compile
into 'libs'
}

build.gradle

buildscript {
repositories {
google()
jcenter()
maven { url 'https://maven.fabric.io/public' }
}
dependencies {
classpath 'com.android.tools.build:gradle:3.1.2'
classpath 'com.google.gms:google-services:3.2.1'
classpath 'io.fabric.tools:gradle:1.+'
}
}

allprojects {
repositories {
mavenLocal()
jcenter()
google()
maven { url "https://jitpack.io" }
maven { url "https://maven.google.com" }
maven {
url "$rootDir/../node_modules/react-native/android"
}
maven { url 'https://maven.fabric.io/public' }
}
}