Minor fixes

app/src/main/java/eu/kanade/tachiyomi/data/database/models/Chapter.java

@@ -87,4 +87,8 @@ public class Chapter implements Serializable {
     public boolean isDownloaded() {
         return status == Download.DOWNLOADED;
     }
+
+    public boolean isRecognizedNumber() {
+        return chapter_number >= 0f;
+    }
 }

app/src/main/java/eu/kanade/tachiyomi/ui/manga/chapter/ChaptersPresenter.kt

@@ -188,7 +188,7 @@ class ChaptersPresenter : BasePresenter<ChaptersFragment>() {
 
     fun markPreviousChaptersAsRead(selected: Chapter) {
         Observable.from(chapters)
-                .filter { it.chapter_number > -1 && it.chapter_number < selected.chapter_number }
+                .filter { it.isRecognizedNumber && it.chapter_number < selected.chapter_number }
                 .doOnNext { it.read = true }
                 .toList()
                 .flatMap { db.updateChaptersProgress(it).asRxObservable() }

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -260,7 +260,7 @@ class ReaderActivity : BaseRxActivity<ReaderPresenter>() {
         page_seekbar.max = numPages - 1
         page_seekbar.progress = currentPage
 
-        setToolbarSubtitle(if (chapter.chapter_number != -1f)
+        setToolbarSubtitle(if (chapter.isRecognizedNumber)
             getString(R.string.chapter_subtitle, decimalFormat.format(chapter.chapter_number.toDouble()))
         else
             chapter.name)

app/src/main/java/eu/kanade/tachiyomi/util/ChapterSourceSync.kt

@@ -71,7 +71,7 @@ fun syncChaptersWithSource(db: DatabaseHelper,
                 val c = toAdd[i]
                 c.date_fetch = now++
                 // Try to mark already read chapters as read when the source deletes them
-                if (c.chapter_number != -1f && c.chapter_number in deletedReadChapterNumbers) {
+                if (c.isRecognizedNumber && c.chapter_number in deletedReadChapterNumbers) {
                     c.read = true
                     readded++
                 }