patch 8.2.1736: failure to compile a pattern not tested much

Problem:    Failure to compile a pattern not tested much.
Solution:   Add tests where a pattern fails to compile. (Yegappan Lakshmanan,
            closes #7004)
diff --git a/src/testdir/test_search_stat.vim b/src/testdir/test_search_stat.vim
index 73cea03..2afccef 100644
--- a/src/testdir/test_search_stat.vim
+++ b/src/testdir/test_search_stat.vim
@@ -260,6 +260,14 @@
 
 func Test_searchcount_fails()
   call assert_fails('echo searchcount("boo!")', 'E715:')
+  call assert_fails('echo searchcount({"timeout" : []})', 'E745:')
+  call assert_fails('echo searchcount({"maxcount" : []})', 'E745:')
+  call assert_fails('echo searchcount({"pattern" : []})', 'E730:')
+  call assert_fails('echo searchcount({"pos" : 1})', 'E475:')
+  call assert_fails('echo searchcount({"pos" : [1]})', 'E475:')
+  call assert_fails('echo searchcount({"pos" : [[], 2, 3]})', 'E745:')
+  call assert_fails('echo searchcount({"pos" : [1, [], 3]})', 'E745:')
+  call assert_fails('echo searchcount({"pos" : [1, 2, []]})', 'E745:')
 endfunc
 
 func Test_searchcount_in_statusline()