Avoid migration failing if previous source doesn't exist

app/src/main/java/eu/kanade/tachiyomi/data/track/EnhancedTrackService.kt

@@ -30,7 +30,7 @@ interface EnhancedTrackService {
     /**
      * Checks whether the provided source/track/manga triplet is from this TrackService
      */
-    fun isTrackFrom(track: Track, manga: Manga, source: Source): Boolean
+    fun isTrackFrom(track: Track, manga: Manga, source: Source?): Boolean
 
     /**
      * Migrates the given track for the manga to the newSource, if possible

app/src/main/java/eu/kanade/tachiyomi/data/track/komga/Komga.kt

@@ -105,8 +105,8 @@ class Komga(private val context: Context, id: Int) : TrackService(id), EnhancedT
             null
         }
 
-    override fun isTrackFrom(track: Track, manga: Manga, source: Source): Boolean =
-        accept(source) && track.tracking_url == manga.url
+    override fun isTrackFrom(track: Track, manga: Manga, source: Source?): Boolean =
+        track.tracking_url == manga.url && source?.let { accept(it) } == true
 
     override fun migrateTrack(track: Track, manga: Manga, newSource: Source): Track? =
         if (accept(newSource)) {

app/src/main/java/eu/kanade/tachiyomi/ui/browse/migration/search/SearchPresenter.kt

@@ -63,8 +63,8 @@ class SearchPresenter(
     }
 
     fun migrateManga(prevManga: Manga, manga: Manga, replace: Boolean) {
-        val prevSource = sourceManager.get(prevManga.source) ?: return
         val source = sourceManager.get(manga.source) ?: return
+        val prevSource = sourceManager.get(prevManga.source)
 
         replacingMangaRelay.call(Pair(true, null))
 
@@ -83,7 +83,7 @@ class SearchPresenter(
     }
 
     private fun migrateMangaInternal(
-        prevSource: Source,
+        prevSource: Source?,
         source: Source,
         sourceChapters: List<SChapter>,
         prevManga: Manga,