Fix an issue where the next chapter was the same as the current. Fix a NPE when page list throws

app/src/main/java/eu/kanade/mangafeed/data/database/DatabaseHelper.java

@@ -188,6 +188,10 @@ public class DatabaseHelper {
     }
 
     public PreparedGetListOfObjects<Chapter> getNextChapter(Chapter chapter) {
+        // Add a delta to the chapter number, because binary decimal representation
+        // can retrieve the same chapter again
+        double chapterNumber = chapter.chapter_number + 0.00001;
+
         return db.get()
                 .listOfObjects(Chapter.class)
                 .withQuery(Query.builder()
@@ -195,7 +199,7 @@ public class DatabaseHelper {
                         .where(ChapterTable.COLUMN_MANGA_ID + "=? AND " +
                                 ChapterTable.COLUMN_CHAPTER_NUMBER + ">? AND " +
                                 ChapterTable.COLUMN_CHAPTER_NUMBER + "<=?")
-                        .whereArgs(chapter.manga_id, chapter.chapter_number, chapter.chapter_number + 1)
+                        .whereArgs(chapter.manga_id, chapterNumber, chapterNumber + 1)
                         .orderBy(ChapterTable.COLUMN_CHAPTER_NUMBER)
                         .limit(1)
                         .build())
@@ -203,6 +207,10 @@ public class DatabaseHelper {
     }
 
     public PreparedGetListOfObjects<Chapter> getPreviousChapter(Chapter chapter) {
+        // Add a delta to the chapter number, because binary decimal representation
+        // can retrieve the same chapter again
+        double chapterNumber = chapter.chapter_number - 0.00001;
+
         return db.get()
                 .listOfObjects(Chapter.class)
                 .withQuery(Query.builder()
@@ -210,7 +218,7 @@ public class DatabaseHelper {
                         .where(ChapterTable.COLUMN_MANGA_ID + "=? AND " +
                                 ChapterTable.COLUMN_CHAPTER_NUMBER + "<? AND " +
                                 ChapterTable.COLUMN_CHAPTER_NUMBER + ">=?")
-                        .whereArgs(chapter.manga_id, chapter.chapter_number, chapter.chapter_number - 1)
+                        .whereArgs(chapter.manga_id, chapterNumber, chapterNumber - 1)
                         .orderBy(ChapterTable.COLUMN_CHAPTER_NUMBER + " DESC")
                         .limit(1)
                         .build())

app/src/main/java/eu/kanade/mangafeed/ui/reader/ReaderActivity.java

@@ -85,7 +85,8 @@ public class ReaderActivity extends BaseRxActivity<ReaderPresenter> {
     @Override
     protected void onDestroy() {
         readerMenu.destroy();
-        viewer.destroy();
+        if (viewer != null)
+            viewer.destroy();
         super.onDestroy();
     }
 
@@ -97,7 +98,8 @@ public class ReaderActivity extends BaseRxActivity<ReaderPresenter> {
 
     @Override
     protected void onPause() {
-        getPresenter().setCurrentPage(viewer.getCurrentPosition());
+        if (viewer != null)
+            getPresenter().setCurrentPage(viewer.getCurrentPosition());
         super.onPause();
     }