Fix thumb extension for webp

app/src/main/kotlin/com/hippo/ehviewer/coil/DownloadThumbInterceptor.kt

@@ -7,7 +7,6 @@ import coil3.request.ImageRequest
 import coil3.request.ImageResult
 import coil3.request.SuccessResult
 import com.hippo.ehviewer.EhApplication.Companion.imageCache
-import com.hippo.ehviewer.download.downloadLocation
 import com.hippo.ehviewer.util.sendTo
 import com.hippo.files.isDirectory
 import com.hippo.files.isFile

app/src/main/kotlin/com/hippo/ehviewer/coil/Extensions.kt

@@ -14,8 +14,10 @@ import com.hippo.ehviewer.download.downloadLocation
 fun ImageRequest.Builder.ehUrl(info: GalleryInfo) = apply {
     val key = info.thumbKey!!
     data(info.thumbUrl)
+    val format = info.thumbUrl.substringAfterLast('.', "")
+    check(format.isNotBlank())
     if (info is DownloadInfo && !info.dirname.isNullOrBlank()) {
-        downloadLocation(downloadLocation / info.dirname / "thumb.jpg")
+        downloadLocation(downloadLocation / info.dirname / "thumb.$format")
     }
     memoryCacheKey(key)
     diskCacheKey(key)