patch 8.2.2244: crash when making the window width negative

Problem:    Crash when making the window width of the not-current window
            negative.
Solution:   Make sure the window width is not negative. (closes #7568)
diff --git a/src/testdir/test_window_cmd.vim b/src/testdir/test_window_cmd.vim
index 51d0722..b0c5a41 100644
--- a/src/testdir/test_window_cmd.vim
+++ b/src/testdir/test_window_cmd.vim
@@ -1148,6 +1148,14 @@
   exe other_winnr .. 'resize +1'
   call assert_equal(12, winheight(other_winnr))
   call assert_equal(&lines - 10 - 3 -2, winheight(0))
+  close
+
+  vsplit
+  wincmd l
+  let other_winnr = winnr('h')
+  call assert_notequal(winnr(), other_winnr)
+  exe 'vert ' .. other_winnr .. 'resize -100'
+  call assert_equal(0, winwidth(other_winnr))
 
   %bwipe!
 endfunc