bug: forgot to create memory usage string when collapsed (#473)

Adds a line to actually build the string of the summed memory usage. I forgot to make the string after summing the values.

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.6.1] - Unreleased
+
+## Bug Fixes
+
+- [#473](https://github.com/ClementTsang/bottom/pull/473): Fix missing string creation for memory usage in collapsed entries.
+
 ## [0.6.0] - 2021-05-09
 
 ## Features

src/data_conversion.rs

@@ -1202,6 +1202,8 @@ pub fn tree_process_data(
                             p.tw_f64 as u64,
                         );
 
+                        p.mem_usage_str = get_binary_bytes(p.mem_usage_bytes);
+
                         p.read_per_sec = disk_io_strings.0;
                         p.write_per_sec = disk_io_strings.1;
                         p.total_read = disk_io_strings.2;