[BUGFIX] use absolute path for thumbnails

Classes/Service/CachedImageService.php

@@ -26,6 +26,7 @@
 
 namespace SGalinski\SgYoutube\Service;
 
+use TYPO3\CMS\Core\Core\Environment;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
 use TYPO3\CMS\Core\Utility\PathUtility;
 
@@ -108,6 +109,12 @@ class CachedImageService {
 		$cachedImageFolderPath = GeneralUtility::getFileAbsFileName(
 			self::CACHED_IMAGES_DIRECTORY . $this->cacheDirectory . '/'
 		);
+
+		// make absolute path, if the $url is a relative path
+		if (strpos($url, '/') === 0) {
+			$url = Environment::getPublicPath() . $url;
+		}
+
 		// Create a hash based on the URL to identify the image
 		$imageHash = \md5($url);
 		// check if any kind of image with this hash is already in the cache-directory