fix: simplify sourceData check

Co-authored-by: Git'Fellow <[email protected]>
Signed-off-by: John Molakvoæ <[email protected]>

lib/private/Files/Cache/Cache.php

@@ -663,7 +663,7 @@ public function moveFromCache(ICache $sourceCache, $sourcePath, $targetPath) {
 			$targetPath = $this->normalize($targetPath);
 
 			$sourceData = $sourceCache->get($sourcePath);
-			if ($sourceData === false || $sourceData === null) {
+			if (!$sourceData) {
 				throw new \Exception('Invalid source storage path: ' . $sourcePath);
 			}