Merge #11467: Fix typos. Use nullptr instead of NULL.

0aacfa4 Remove accidental stray semicolon (practicalswift)
68feb49 Use nullptr instead of NULL (practicalswift)
c6b07fd Fix a vs. an typo (practicalswift)

Pull request description:

  Minor cleanups:
  * Typo: Fix a vs. an typo
  * Typo: Remove accidental stray semicolon (only remaining instance in repo)
  * Correctness/consistency: Use `nullptr` instead of `NULL` (only remaining instance in repo)

Tree-SHA512: 47142e557da9d3fa0b532c46edeb7f356a1f6dc5973e60b0e496badff3581ff696eade542d49da777ac7f2e895129cc8487ccdb1984ff828434fa86f9a56dad0

src/wallet/wallet.cpp

@@ -3881,7 +3881,7 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
         // Top up the keypool
         if (!walletInstance->TopUpKeyPool()) {
             InitError(_("Unable to generate initial keys") += "\n");
-            return NULL;
+            return nullptr;
         }
 
         walletInstance->SetBestChain(chainActive.GetLocator());