fix(installer): throw an exception only if app store is also enabled

Signed-off-by: Kent Delante <kent@delante.me>

Author: leftybournes

lib/private/Installer.php

@@ -136,7 +136,7 @@ public function getInstallPath(): ?string {
 		foreach (\OC::$APPSROOTS as $dir) {
 			if (isset($dir['writable']) && $dir['writable'] === true) {
 				// Check if there is a writable install folder.
-				if (!is_writable($dir['path'])
+				if ((!is_writable($dir['path']) && $this->config->getSystemValueBool('appstoreenabled', true))
 					|| !is_readable($dir['path'])
 				) {
 					throw new \RuntimeException(