[t:5013] don't initialize dest_val if src_val is empty in tokudb_generate_row...

[t:5013] don't initialize dest_val if src_val is empty in tokudb_generate_row on mainline too.  fixes #5013

git-svn-id: file:///svn/mysql/tokudb-engine/tokudb-engine@44256 c7de825b-a66e-492c-adef-691d508d4ae1

storage/tokudb/ha_tokudb.cc

@@ -1151,7 +1151,7 @@ static inline int tokudb_generate_row(
     desc_size = (*(u_int32_t *)row_desc) - 4;
     row_desc += 4;
     if (dest_val != NULL) {
-        if (!is_key_clustering(row_desc, desc_size)) {
+        if (!is_key_clustering(row_desc, desc_size) || src_val->size == 0) {
             dest_val->size = 0;
         }
         else {