Unexpected node Android Packaging in Android Gradl

I am trying to make my project use gradle. The problem is that everytime I try to build, I get the following error:

Error:Internal error: (java.lang.AssertionError) Unexpected node Android Packaging; nodes=[Module 'Serengeti' production, Resources for 'Serengeti' production, Resources for 'Serengeti' tests, Artifact 'Serengeti', gradle-resources-production:Serengeti, gradle-resources-test:Serengeti, Android Gradle Build Target]
java.lang.AssertionError: Unexpected node Android Packaging; nodes=[Module 'Serengeti' production, Resources for 'Serengeti' production, Resources for 'Serengeti' tests, Artifact 'Serengeti', gradle-resources-production:Serengeti, gradle-resources-test:Serengeti, Android Gradle Build Target]
    at com.intellij.util.graph.GraphGenerator.buildOuts(GraphGenerator.java:55)
    at com.intellij.util.graph.GraphGenerator.<init>(GraphGenerator.java:36)
    at com.intellij.util.graph.GraphGenerator.create(GraphGenerator.java:40)
    at org.jetbrains.jps.builders.impl.BuildTargetIndexImpl.initializeChunks(BuildTargetIndexImpl.java:86)
    at org.jetbrains.jps.builders.impl.BuildTargetIndexImpl.getSortedTargetChunks(BuildTargetIndexImpl.java:50)
    at org.jetbrains.jps.incremental.IncProjectBuilder.buildChunks(IncProjectBuilder.java:610)
    at org.jetbrains.jps.incremental.IncProjectBuilder.runBuild(IncProjectBuilder.java:352)
    at org.jetbrains.jps.incremental.IncProjectBuilder.build(IncProjectBuilder.java:191)
    at org.jetbrains.jps.cmdline.BuildRunner.runBuild(BuildRunner.java:131)
    at org.jetbrains.jps.cmdline.BuildSession.runBuild(BuildSession.java:229)
    at org.jetbrains.jps.cmdline.BuildSession.run(BuildSession.java:113)
    at org.jetbrains.jps.cmdline.BuildMain$MyMessageHandler$1.run(BuildMain.java:158)
    at org.jetbrains.jps.service.impl.SharedThreadPoolImpl$1.run(SharedThreadPoolImpl.java:41)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)

I have no idea what this means. I found this but it's not really helpful...

This is my build.gradle file. This is my first time using gradle so if there is anything wrong with this please point it out.

buildscript {
    repositories {
        mavenCentral()
        maven { url 'https://maven.fabric.io/repo' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.14.+'
        classpath 'io.fabric.tools:gradle:1.+'
    }
}
apply plugin: 'android'
apply plugin: 'io.fabric'

repositories {
    mavenCentral()
    maven { url 'https://maven.fabric.io/repo' }
}

dependencies {
    // http://gradleplease.appspot.com/
    compile 'com.android.support:support-v4:20.+'
    compile 'com.google.android.gms:play-services:+'
    compile 'joda-time:joda-time:+'
    compile 'com.googlecode.android-query:android-query:+'
    compile 'me.dm7.barcodescanner:zbar:+'
    compile 'com.github.asne.facebook:facebook:3.17.2'
    compile('com.twitter.sdk.android:twitter:1.0.1@aar') {
        transitive = true;
    }
}

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.1"
    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 21
    }
    lintOptions {
        abortOnError false
    }
    signingConfigs {
        SignConfig {
            keyAlias 'removed'
            keyPassword 'removed'
            storeFile file('removed')
            storePassword 'removed'
        }
    }
    buildTypes {
        debug {
            sourceSets {
                main {
                    manifest.srcFile 'AndroidManifest.xml'
                    java.srcDirs = ['src']
                    resources.srcDirs = ['src']
                    aidl.srcDirs = ['src']
                    renderscript.srcDirs = ['src']
                    res.srcDirs = ['res']
                    assets.srcDirs = ['assets']
                }
            }
        }

        release {
            zipAlignEnabled
            sourceSets {
                main {
                    manifest.srcFile 'AndroidManifest.xml'
                    java.srcDirs = ['src']
                    resources.srcDirs = ['src']
                    aidl.srcDirs = ['src']
                    renderscript.srcDirs = ['src']
                    res.srcDirs = ['res']
                    assets.srcDirs = ['assets']
                }
            }
        }
    }
    productFlavors {
        RunConfig {
            signingConfig signingConfigs.SignConfig
        }
    }
}

How can I fix this error?

Found the solution to this problem. If you go to Project Structure -> Modules -> <Your project> -> Android, you will notice that nothing loads. It will look like this:

In order to fix this, select Android and click Remove (the red dash above). Then click Add (the green plus above) and select Android. Click OK and the error should be gone now.