Fix NPE on media message with no media.

Fixes #3921
// FREEBIE

src/org/thoughtcrime/securesms/components/ThumbnailView.java

@@ -21,7 +21,6 @@ import android.widget.ImageView;
 import com.bumptech.glide.DrawableTypeRequest;
 import com.bumptech.glide.GenericRequestBuilder;
 import com.bumptech.glide.Glide;
-import com.bumptech.glide.load.resource.bitmap.CenterCrop;
 import com.bumptech.glide.load.resource.bitmap.GlideBitmapDrawable;
 import com.bumptech.glide.load.resource.drawable.GlideDrawable;
 import com.bumptech.glide.request.RequestListener;
@@ -32,11 +31,11 @@ import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.crypto.MasterSecret;
 import org.thoughtcrime.securesms.jobs.PartProgressEvent;
 import org.thoughtcrime.securesms.mms.DecryptableStreamUriLoader.DecryptableUri;
+import org.thoughtcrime.securesms.mms.RoundedCorners;
 import org.thoughtcrime.securesms.mms.Slide;
 import org.thoughtcrime.securesms.mms.SlideDeck;
 import org.thoughtcrime.securesms.util.FutureTaskListener;
 import org.thoughtcrime.securesms.util.ListenableFutureTask;
-import org.thoughtcrime.securesms.mms.RoundedCorners;
 import org.thoughtcrime.securesms.util.Util;
 
 import de.greenrobot.event.EventBus;
@@ -245,7 +244,8 @@ public class ThumbnailView extends FrameLayout {
     public void onSuccess(final SlideDeck slideDeck) {
       if (slideDeck == null) return;
 
-      final Slide slide = slideDeck.getThumbnailSlide(getContext());
+      final Slide slide = slideDeck.getThumbnailSlide();
+
       if (slide != null) {
         Util.runOnMain(new Runnable() {
           @Override

src/org/thoughtcrime/securesms/mms/SlideDeck.java

@@ -18,6 +18,7 @@ package org.thoughtcrime.securesms.mms;
 
 import android.content.Context;
 import android.graphics.drawable.Drawable;
+import android.support.annotation.Nullable;
 import android.util.Pair;
 
 import org.thoughtcrime.securesms.R;
@@ -89,7 +90,7 @@ public class SlideDeck {
     return false;
   }
 
-  public Slide getThumbnailSlide(Context context) {
+  public @Nullable Slide getThumbnailSlide() {
     for (Slide slide : slides) {
       if (slide.hasImage()) {
         return slide;

src/org/thoughtcrime/securesms/notifications/SingleRecipientNotificationBuilder.java

@@ -21,6 +21,7 @@ import com.bumptech.glide.Glide;
 import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.crypto.MasterSecret;
 import org.thoughtcrime.securesms.mms.DecryptableStreamUriLoader;
+import org.thoughtcrime.securesms.mms.Slide;
 import org.thoughtcrime.securesms.mms.SlideDeck;
 import org.thoughtcrime.securesms.preferences.NotificationPrivacyPreference;
 import org.thoughtcrime.securesms.recipients.Recipient;
@@ -167,12 +168,17 @@ public class SingleRecipientNotificationBuilder extends AbstractNotificationBuil
 
   private boolean hasBigPictureSlide(@Nullable ListenableFutureTask<SlideDeck> slideDeck) {
     try {
-      return masterSecret != null                                        &&
+      if (masterSecret == null || slideDeck == null || Build.VERSION.SDK_INT < 16) {
-             slideDeck != null                                           &&
+        return false;
-             Build.VERSION.SDK_INT >= 16                                 &&
+      }
-             slideDeck.get().getThumbnailSlide(context).hasImage()       &&
+
-             !slideDeck.get().getThumbnailSlide(context).isInProgress()  &&
+      Slide thumbnailSlide = slideDeck.get().getThumbnailSlide();
-             slideDeck.get().getThumbnailSlide(context).getThumbnailUri() != null;
+
+      return thumbnailSlide != null         &&
+             thumbnailSlide.hasImage()      &&
+             !thumbnailSlide.isInProgress() &&
+             thumbnailSlide.getThumbnailUri() != null;
+
     } catch (InterruptedException | ExecutionException e) {
       Log.w(TAG, e);
       return false;
@@ -183,7 +189,7 @@ public class SingleRecipientNotificationBuilder extends AbstractNotificationBuil
                                @NonNull ListenableFutureTask<SlideDeck> slideDeck)
   {
     try {
-      Uri uri = slideDeck.get().getThumbnailSlide(context).getThumbnailUri();
+      Uri uri = slideDeck.get().getThumbnailSlide().getThumbnailUri();
 
       return Glide.with(context)
                   .load(new DecryptableStreamUriLoader.DecryptableUri(masterSecret, uri))