mtr_t::log_file_op(): Fix -Wnonnull

GCC 12.2.0 could issue -Wnonnull for an unreachable call to
strlen(new_path).  Let us prevent that by replacing the condition
(type == FILE_RENAME) with the equivalent (new_path).
This should also optimize the generated code, because the life time
of the parameter "type" will be reduced.

storage/innobase/fil/fil0fil.cc

@@ -1554,17 +1554,18 @@ inline void mtr_t::log_file_op(mfile_type_t type, ulint space_id,
   m_last= nullptr;
 
   const size_t len= strlen(path);
-  const size_t new_len= type == FILE_RENAME ? 1 + strlen(new_path) : 0;
+  const size_t new_len= new_path ? 1 + strlen(new_path) : 0;
   ut_ad(len > 0);
   byte *const log_ptr= m_log.open(1 + 3/*length*/ + 5/*space_id*/ +
                                   1/*page_no=0*/);
+  *log_ptr= type;
   byte *end= log_ptr + 1;
   end= mlog_encode_varint(end, space_id);
   *end++= 0;
-  if (UNIV_LIKELY(end + len + new_len >= &log_ptr[16]))
+  const byte *const final_end= end + len + new_len;
+  if (UNIV_LIKELY(final_end >= &log_ptr[16]))
   {
-    *log_ptr= type;
-    size_t total_len= len + new_len + end - log_ptr - 15;
+    size_t total_len= final_end - log_ptr - 15;
     if (total_len >= MIN_3BYTE)
       total_len+= 2;
     else if (total_len >= MIN_2BYTE)
@@ -1575,13 +1576,13 @@ inline void mtr_t::log_file_op(mfile_type_t type, ulint space_id,
   }
   else
   {
-    *log_ptr= static_cast<byte>(type | (end + len + new_len - &log_ptr[1]));
+    *log_ptr= static_cast<byte>(*log_ptr | (final_end - &log_ptr[1]));
     ut_ad(*log_ptr & 15);
   }
 
   m_log.close(end);
 
-  if (type == FILE_RENAME)
+  if (new_path)
   {
     ut_ad(strchr(new_path, OS_PATH_SEPARATOR));
     m_log.push(reinterpret_cast<const byte*>(path), uint32_t(len + 1));