[BUGFIX] Prevent RegisterService from crashing if no mail template have been registered

Classes/Service/RegisterService.php

@@ -95,21 +95,23 @@ class RegisterService implements \TYPO3\CMS\Core\SingletonInterface {
 	private function registerExtensions(): array {
 		$this->registerArray = [];
 
-		foreach ($GLOBALS['sg_mail'] as $extensionName => $templates) {
-			foreach ($templates as $templateKey => $registerFile) {
-				$registerFile = GeneralUtility::getFileAbsFileName($registerFile);
-				if (!\is_file($registerFile)) {
-					continue;
-				}
-
-				$configArray = (include $registerFile);
-				$extensionKey = $configArray['extension_key'];
-				$templateKey = $configArray['template_key'];
-				if ($extensionKey === NULL) {
-					continue;
+		if (\is_array($GLOBALS['sg_mail'])) {
+			foreach ($GLOBALS['sg_mail'] as $extensionName => $templates) {
+				foreach ($templates as $templateKey => $registerFile) {
+					$registerFile = GeneralUtility::getFileAbsFileName($registerFile);
+					if (!\is_file($registerFile)) {
+						continue;
+					}
+
+					$configArray = (include $registerFile);
+					$extensionKey = $configArray['extension_key'];
+					$templateKey = $configArray['template_key'];
+					if ($extensionKey === NULL) {
+						continue;
+					}
+
+					$this->writeRegisterArrayEntry($extensionKey, $templateKey, $configArray);
 				}
-
-				$this->writeRegisterArrayEntry($extensionKey, $templateKey, $configArray);
 			}
 		}