clang-tidy: Enable modernize-use-nullptr

Modified code to address issues flagged by this check.

Tested: Build and unit tests passed successfully.

Change-Id: Idd4daacdcb998d49b938b1d2a194084781d11e96
Signed-off-by: Jayanth Othayoth <ojayanth@gmail.com>
diff --git a/.clang-tidy b/.clang-tidy
index ee5b55f..549f4c9 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -289,6 +289,7 @@
 modernize-use-equals-default,
 modernize-use-equals-delete,
 modernize-use-noexcept,
+modernize-use-nullptr,
 modernize-use-starts-ends-with,
 modernize-use-std-numbers,
 modernize-use-transparent-functors,
diff --git a/certs_manager.cpp b/certs_manager.cpp
index 2084f3a..7e50e88 100644
--- a/certs_manager.cpp
+++ b/certs_manager.cpp
@@ -849,8 +849,8 @@
         lg2::error("Error occurred creating private key file");
         elog<InternalFailure>();
     }
-    int ret =
-        PEM_write_PrivateKey(fp, pKey.get(), nullptr, nullptr, 0, 0, nullptr);
+    int ret = PEM_write_PrivateKey(fp, pKey.get(), nullptr, nullptr, 0, nullptr,
+                                   nullptr);
     std::fclose(fp);
     if (ret == 0)
     {