[BUGFIX] Catch exception when fetching external image

The fetching of an external file with GeneralUtility::getUrl()
may throw an exception if the image is not available (at least
since Guzzle is used internally with TYPO3 and libcurl is installed).

The exception is now caught. If the exception occurs no further
processing on the image is done.

Resolves: netresearch#190

Classes/Database/RteImagesDbHook.php

@@ -205,7 +205,12 @@ public function transform_db($value)
                     ) {
                         // External image from another URL: in that case, fetch image, unless the feature is disabled or we are not in backend mode
                         // Fetch the external image
-                        $externalFile = GeneralUtility::getUrl($absoluteUrl);
+                        $externalFile = null;
+                        try {
+                            $externalFile = GeneralUtility::getUrl($absoluteUrl);
+                        } catch (\Throwable $e) {
+                            // do nothing, further image processing will be skipped
+                        }
                         if ($externalFile) {
                             $pU = parse_url($absoluteUrl);
                             $path = is_array($pU) ? ($pU['path'] ?? '') : '';