key_ cannot become nullptr, so no check is needed for that

(ignoring the unlikely case that some overrides
`operator new throw(std::bad_alloc)` with a function that returns a nullptr)

db/dbformat.h

@@ -302,7 +302,7 @@ class IterKey {
       char* p = new char[total_size];
       memcpy(p, key_, shared_len);
 
-      if (key_ != nullptr && key_ != space_) {
+      if (key_ != space_) {
         delete[] key_;
       }
 
@@ -388,10 +388,10 @@ class IterKey {
   char space_[32];  // Avoid allocation for short keys
 
   void ResetBuffer() {
-    if (key_ != nullptr && key_ != space_) {
+    if (key_ != space_) {
       delete[] key_;
+      key_ = space_;
     }
-    key_ = space_;
     buf_size_ = sizeof(space_);
     key_size_ = 0;
   }