Small improvement

app/src/main/java/eu/faircode/email/ActivityView.java

@@ -1530,7 +1530,7 @@ public class ActivityView extends ActivityBilling implements FragmentManager.OnB
                 DB db = DB.getInstance(context);
                 EntityAttachment attachment = db.attachment().getAttachment(id);
                 if (attachment == null)
-                    throw new FileNotFoundException();
+                    return null;
                 File file = attachment.getFile(context);
 
                 ParcelFileDescriptor pfd = null;

app/src/main/java/eu/faircode/email/AdapterAttachment.java

@@ -38,7 +38,6 @@ import android.widget.TextView;
 import android.widget.Toast;
 
 import java.io.File;
-import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -174,7 +173,7 @@ public class AdapterAttachment extends RecyclerView.Adapter<AdapterAttachment.Vi
                     DB db = DB.getInstance(context);
                     EntityAttachment attachment = db.attachment().getAttachment(id);
                     if (attachment == null)
-                        throw new FileNotFoundException();
+                        return null;
                     db.attachment().setDownloaded(id, null);
                     attachment.getFile(context).delete();
                     db.attachment().deleteAttachment(id);

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -27,7 +27,6 @@ import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
-import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.FileReader;
 import java.io.IOException;
@@ -712,7 +711,7 @@ public class MessageHelper {
             AttachmentPart apart = attachments.get(index);
             EntityAttachment attachment = db.attachment().getAttachment(id);
             if (attachment == null)
-                throw new FileNotFoundException();
+                return;
             File file = attachment.getFile(context);
 
             // Download attachment