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)

src/testdir/test_window_cmd.vim

@@ -1148,6 +1148,14 @@ func Test_window_resize()
   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

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2244,
 /**/
     2243,
 /**/

src/window.c

@@ -5687,6 +5687,8 @@ win_setwidth_win(int width, win_T *wp)
 	if (width == 0)
 	    width = 1;
     }
+    else if (width < 0)
+	width = 0;
 
     frame_setwidth(wp->w_frame, width + wp->w_vsep_width);