Fix crash on source page load error

app/src/main/java/eu/kanade/tachiyomi/ui/browse/source/browse/BrowseSourcePresenter.kt

@@ -180,7 +180,7 @@ open class BrowseSourcePresenter(
             try {
                 pager.requestNextPage()
             } catch (e: Throwable) {
-                view?.onAddPageError(e)
+                withUIContext { view?.onAddPageError(e) }
             }
         }
     }