Update miniz.h

Fix test against null bytes to push back.

contrib/zip/src/miniz.h

@@ -3030,10 +3030,8 @@ static MZ_FORCEINLINE mz_bool mz_zip_array_ensure_room(mz_zip_archive *pZip, mz_
 
 static MZ_FORCEINLINE mz_bool mz_zip_array_push_back(mz_zip_archive *pZip, mz_zip_array *pArray, const void *pElements, size_t n)
 {
-//  assert(NULL != pElements);
-  if (pElements == NULL) {
-      return MZ_TRUE;
-  }
+  if (n==0) return MZ_TRUE;
+  assert(NULL != pElements);
   size_t orig_size = pArray->m_size; if (!mz_zip_array_resize(pZip, pArray, orig_size + n, MZ_TRUE)) return MZ_FALSE;
   memcpy((mz_uint8*)pArray->m_p + orig_size * pArray->m_element_size, pElements, n * pArray->m_element_size);
   return MZ_TRUE;