animated gifs can not be transformed to the webp format

We can't efficiently check if the input is an animated gif, therefore we
catch the exception and try to convert to gif if converting to webp
failed.

Imagine/Filter/FilterManager.php

@@ -160,7 +160,17 @@ private function exportConfiguredImageBinary(BinaryInterface $binary, ImageInter
         }
 
         $filteredFormat = $config['format'] ?? $binary->getFormat();
-        $filteredString = $image->get($filteredFormat, $options);
+        try {
+            $filteredString = $image->get($filteredFormat, $options);
+        } catch (\Exception $exception) {
+            // we don't support converting an animated gif into webp.
+            // we can't efficiently check the input data, therefore we retry with target format gif in case of an error.
+            if ('webp' !== $filteredFormat || !\array_key_exists('animated', $options) || true !== $options['animated']) {
+                throw $exception;
+            }
+            $filteredFormat = 'gif';
+            $filteredString = $image->get($filteredFormat, $options);
+        }
 
         $this->destroyImage($image);