patch 8.1.1642: may use uninitialized variable

Problem:    May use uninitialized variable. (Patrick Palka)
Solution:   Initialize variables earlier. (closes #4623)
diff --git a/src/testdir/test_number.vim b/src/testdir/test_number.vim
index 415aefc..81326bc 100644
--- a/src/testdir/test_number.vim
+++ b/src/testdir/test_number.vim
@@ -252,3 +252,14 @@
   call s:compare_lines(expect, lines)
   call s:close_windows()
 endfunc
+
+" This was causing a memcheck error
+func Test_relativenumber_uninitialised()
+  new
+  set rnu
+  call setline(1, ["a", "b"])
+  redraw
+  call feedkeys("j", 'xt')
+  redraw
+  bwipe!
+endfunc