Merge pull request #30971 from nextcloud/backport/stable22/office_pre…

…view

Fix preview generation for office documents

lib/private/Preview/Office.php

@@ -74,7 +74,7 @@ public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage {
 		}
 
 		$image = new \OC_Image();
-		$image->loadFromData($png);
+		$image->loadFromData((string) $png);
 
 		$this->cleanTmpFiles();
 		unlink($pngPreview);