Nullability checks

extractToByteBuffer may return null object for some reason

app/src/main/java/com/hippo/UriArchiveAccessor.kt

@@ -28,7 +28,7 @@ class UriArchiveAccessor(ctx: Context, uri: Uri) {
     }
 
     private external fun openArchive(fd: Int, size: Long): Int
-    external fun extractToByteBuffer(index: Int): ByteBuffer
+    external fun extractToByteBuffer(index: Int): ByteBuffer?
 
     external fun releaseByteBuffer(buffer: ByteBuffer)
     external fun extractToFd(index: Int, fd: Int)

app/src/main/java/com/hippo/ehviewer/gallery/ArchiveGalleryProvider.java

@@ -333,11 +333,13 @@ public class ArchiveGalleryProvider extends GalleryProvider2 {
                     buffer = entry.getValue();
                 }
 
-                Image image;
-                image = Image.decode(buffer, false, () -> {
-                    archiveAccessor.releaseByteBuffer(buffer);
-                    return null;
-                });
+                Image image = null;
+                if (buffer != null) {
+                    image = Image.decode(buffer, false, () -> {
+                        archiveAccessor.releaseByteBuffer(buffer);
+                        return null;
+                    });
+                }
                 if (image != null) {
                     notifyPageSucceed(index, image);
                 } else {