MultiDexApplication not found at app launch
<p>As so many times before, Android Studio suggested to install some upgrades, which I did. Now my app crashes at launch:</p>

<pre><code>java.lang.RuntimeException: Unable to instantiate application android.support.multidex.MultiDexApplication: java.lang.ClassNotFoundException: Didn't find class "android.support.multidex.MultiDexApplication" on path: DexPathList[[zip file "/system/framework/com.google.android.maps.jar", zip file "/data/app/com.bluelionsolutions.dfhv-2/base.apk"],nativeLibraryDirectories=[/data/app/com.bluelionsolutions.dfhv-2/lib/arm, /vendor/lib, /system/lib]]
                  at android.app.LoadedApk.makeApplication(LoadedApk.java:587)
                  at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4932)
                  at android.app.ActivityThread.-wrap1(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1549)
                  at android.os.Handler.dispatchMessage(Handler.java:111)
                  at android.os.Looper.loop(Looper.java:207)
                  at android.app.ActivityThread.main(ActivityThread.java:5728)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:679)
</code></pre>

<p>Absolutely no clue what the problem could be.
Help is very much appreciated.</p>