Modernize codebase by replacing NULL with nullptr

Fixes -Wzero-as-null-pointer-constant warning.

Test: m
Bug: 68236239
Change-Id: I5b4123bc6709641315120a191e36cc57541349b2
diff --git a/libc/malloc_debug/malloc_debug.cpp b/libc/malloc_debug/malloc_debug.cpp
index 2e3a0a3..9075a9c 100644
--- a/libc/malloc_debug/malloc_debug.cpp
+++ b/libc/malloc_debug/malloc_debug.cpp
@@ -284,7 +284,7 @@
   ScopedDisableDebugCalls disable;
 
   // Verify the arguments.
-  if (info == nullptr || overall_size == nullptr || info_size == NULL || total_memory == nullptr ||
+  if (info == nullptr || overall_size == nullptr || info_size == nullptr || total_memory == nullptr ||
       backtrace_size == nullptr) {
     error_log("get_malloc_leak_info: At least one invalid parameter.");
     return;