patch 8.2.2994: various code is not fully tested

Problem:    Various code is not fully tested.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #8378)
diff --git a/src/testdir/test_excmd.vim b/src/testdir/test_excmd.vim
index de82b5b..514a4cf 100644
--- a/src/testdir/test_excmd.vim
+++ b/src/testdir/test_excmd.vim
@@ -596,7 +596,7 @@
   " some options cannot be changed in a sandbox
   call assert_fails('set exrc', 'E48:')
   call assert_fails('set cdpath', 'E48:')
-  if has('xim')
+  if has('xim') && has('gui_gtk')
     call assert_fails('set imstyle', 'E48:')
   endif
 endfunc