src: add null check to GetCategoryGroupEnabled()

The input to this function shouldn't be null, and callers are
not equipped to deal with a nullptr return value. Change the
nullptr return to a CHECK_NOT_NULL(). Also fix the indentation
of the function.

PR-URL: #21545
Fixes: #19991
Reviewed-By: Wyatt Preul <wpreul@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

src/node_trace_events.cc

@@ -95,9 +95,8 @@ static std::unordered_set<std::string> categoryGroups;
 // Gets a pointer to the category-enabled flags for a tracing category group,
 // if tracing is enabled for it.
 static const uint8_t* GetCategoryGroupEnabled(const char* category_group) {
-    if (category_group == nullptr) return nullptr;
-
-    return TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(category_group);
+  CHECK_NOT_NULL(category_group);
+  return TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(category_group);
 }
 
 static const char* GetCategoryGroup(Environment* env,