Ticket #35521: 35521.2.diff

src/wp-admin/theme-install.php

@@ -28 +28 @@
 }
 
 $installed_themes = search_theme_directories();
+
+if ( false === $installed_themes ) {
+        $installed_themes = array();
+}
+
 foreach ( $installed_themes as $k => $v ) {
         if ( false !== strpos( $k, '/' ) ) {
                 unset( $installed_themes[ $k ] );