patch 8.2.0644: insufficient testing for invalid function arguments

Problem:    Insufficient testing for invalid function arguments.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5988)
diff --git a/src/testdir/test_window_cmd.vim b/src/testdir/test_window_cmd.vim
index 4927842..e20bfa5 100644
--- a/src/testdir/test_window_cmd.vim
+++ b/src/testdir/test_window_cmd.vim
@@ -445,6 +445,7 @@
   call assert_equal([1, 32], win_screenpos(2))
   call assert_equal([12, 1], win_screenpos(3))
   call assert_equal([0, 0], win_screenpos(4))
+  call assert_fails('let l = win_screenpos([])', 'E745:')
   only
 endfunc
 
@@ -694,6 +695,7 @@
 
   only!
   bwipe!
+  call assert_fails('call winrestview(test_null_dict())', 'E474:')
 endfunc
 
 func Test_relative_cursor_position_after_move_and_resize()
@@ -870,6 +872,10 @@
   call assert_fails("echo winnr('ll')", 'E15:')
   call assert_fails("echo winnr('5')", 'E15:')
   call assert_equal(4, winnr('0h'))
+  call assert_fails("let w = winnr([])", 'E730:')
+  call assert_equal('unknown', win_gettype(-1))
+  call assert_equal(-1, winheight(-1))
+  call assert_equal(-1, winwidth(-1))
 
   tabnew
   call assert_equal(8, tabpagewinnr(1, 'j'))
@@ -890,6 +896,7 @@
   call assert_equal(view, winsaveview())
 
   bwipe!
+  call assert_fails('call winrestview(test_null_dict())', 'E474:')
 endfunc
 
 func Test_win_splitmove()
@@ -920,6 +927,7 @@
   call assert_equal(bufname(winbufnr(2)), 'b')
   call assert_equal(bufname(winbufnr(3)), 'a')
   call assert_equal(bufname(winbufnr(4)), 'd')
+  call assert_fails('call win_splitmove(winnr(), winnr("k"), test_null_dict())', 'E474:')
   only | bd
 
   call assert_fails('call win_splitmove(winnr(), 123)', 'E957:')