refs #5876 always init pad_char to avoid erroneous compiler warning

git-svn-id: file:///svn/mysql/tokudb-engine/tokudb-engine@51837 c7de825b-a66e-492c-adef-691d508d4ae1

storage/tokudb/ha_tokudb_alter_56.cc

@@ -790,6 +790,7 @@ int ha_tokudb::alter_table_expand_one_column(TABLE *altered_table, Alter_inplace
             operation = UPDATE_OP_EXPAND_UINT;
         else
             operation = UPDATE_OP_EXPAND_INT;
+        pad_char = 0;
         break;
     case toku_type_fixstring:
         operation = UPDATE_OP_EXPAND_CHAR;