Fix debug heap chunk length.

Change-Id: I1a51f26ec1ce173df35f5fd9502ad32050111d06
diff --git a/src/debugger.cc b/src/debugger.cc
index e928b46..2fa77ef 100644
--- a/src/debugger.cc
+++ b/src/debugger.cc
@@ -2691,7 +2691,7 @@
         reinterpret_cast<const void*>(reinterpret_cast<const char*>(const_cast<void*>(start)) -
             (2 * sizeof(size_t)));
     // from malloc.c chunksize
-    size_t chunk_len = (*reinterpret_cast<size_t* const*>(chunk_ptr))[1] & ~7;
+    size_t chunk_len = (reinterpret_cast<size_t const*>(chunk_ptr))[1] & ~7;
 
 
     //size_t chunk_len = malloc_usable_size(user_ptr);