patch 8.2.0573: using :version twice leaks memory

Problem:    using :version twice leaks memory
Solution:   Only initialize variables once. (Dominique Pelle, closes #5917)
diff --git a/src/testdir/test_version.vim b/src/testdir/test_version.vim
new file mode 100644
index 0000000..2f66f50
--- /dev/null
+++ b/src/testdir/test_version.vim
@@ -0,0 +1,10 @@
+" Test :version Ex command
+
+func Test_version()
+  " version should always return the same string.
+  let v1 = execute('version')
+  let v2 = execute('version')
+  call assert_equal(v1, v2)
+
+  call assert_match("^\n\nVIM - Vi IMproved .*", v1)
+endfunc