fixed crash for no author

alexandria/CHANGELOG.md

@@ -2,4 +2,6 @@
 * Fixed NPE if the device is offline
 * Fixed missing whitespace in share_text string
 * Changed about fragment appearance
-* Fixed NPE when rotating device in BookDetail fragment by retaining it
+* Fixed NPE when rotating device in BookDetail fragment by retaining it
+
+* Fixed crash if a book has no author

alexandria/app/src/main/java/it/jaschke/alexandria/AddBook.java

@@ -169,7 +169,10 @@ public class AddBook extends Fragment implements LoaderManager.LoaderCallbacks<C
         ((TextView) rootView.findViewById(R.id.bookSubTitle)).setText(bookSubTitle);
 
         String authors = data.getString(data.getColumnIndex(AlexandriaContract.AuthorEntry.AUTHOR));
-        String[] authorsArr = authors.split(",");
+        if(authors == null)
+            authors = "";
+        String[] authorsArr;
+        authorsArr = authors.split(",");
         ((TextView) rootView.findViewById(R.id.authors)).setLines(authorsArr.length);
         ((TextView) rootView.findViewById(R.id.authors)).setText(authors.replace(",","\n"));
         String imgUrl = data.getString(data.getColumnIndex(AlexandriaContract.BookEntry.IMAGE_URL));