Fix deref after null

ctx may be NULL at 178 line

CLA: trivial

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17293)
diff --git a/providers/implementations/storemgmt/file_store.c b/providers/implementations/storemgmt/file_store.c
index 340b01b..dc93f08 100644
--- a/providers/implementations/storemgmt/file_store.c
+++ b/providers/implementations/storemgmt/file_store.c
@@ -175,7 +175,7 @@
 
     if ((ctx = new_file_ctx(IS_DIR, uri, provctx)) == NULL) {
         ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
-        goto err;
+        return NULL;
     }
 
     ctx->_.dir.last_entry = OPENSSL_DIR_read(&ctx->_.dir.ctx, path);