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_functions.vim b/src/testdir/test_functions.vim
index a0807ad..02b6585 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -29,6 +29,8 @@
     call assert_equal(0, and(has('ttyout'), 0))
     call assert_equal(1, has('multi_byte_encoding'))
   endif
+  call assert_equal(1, has('vcon', 1))
+  call assert_equal(1, has('mouse_gpm_enabled', 1))
 
   call assert_equal(0, has('nonexistent'))
   call assert_equal(0, has('nonexistent', 1))
@@ -1304,12 +1306,15 @@
 
 " Test for the inputdialog() function
 func Test_inputdialog()
-  CheckNotGui
-
-  call feedkeys(":let v=inputdialog('Q:', 'xx', 'yy')\<CR>\<CR>", 'xt')
-  call assert_equal('xx', v)
-  call feedkeys(":let v=inputdialog('Q:', 'xx', 'yy')\<CR>\<Esc>", 'xt')
-  call assert_equal('yy', v)
+  if has('gui_running')
+    call assert_fails('let v=inputdialog([], "xx")', 'E730:')
+    call assert_fails('let v=inputdialog("Q", [])', 'E730:')
+  else
+    call feedkeys(":let v=inputdialog('Q:', 'xx', 'yy')\<CR>\<CR>", 'xt')
+    call assert_equal('xx', v)
+    call feedkeys(":let v=inputdialog('Q:', 'xx', 'yy')\<CR>\<Esc>", 'xt')
+    call assert_equal('yy', v)
+  endif
 endfunc
 
 " Test for inputlist()
@@ -1344,6 +1349,7 @@
     call balloon_show('hi!')
     if !has('gui_running')
       call balloon_show(range(3))
+      call balloon_show([])
     endif
   endif
 endfunc
@@ -2213,6 +2219,9 @@
   call assert_fails('let x=range(2, 8, 0)', 'E726:')
   call assert_fails('let x=range(3, 1)', 'E727:')
   call assert_fails('let x=range(1, 3, -2)', 'E727:')
+  call assert_fails('let x=range([])', 'E745:')
+  call assert_fails('let x=range(1, [])', 'E745:')
+  call assert_fails('let x=range(1, 4, [])', 'E745:')
 endfunc
 
 func Test_echoraw()