patch 8.2.0407: no early check if :find and :sfind have an argument

Problem:    No early check if :find and :sfind have an argument.
Solution:   Add EX_NEEDARG.
diff --git a/src/testdir/test_find_complete.vim b/src/testdir/test_find_complete.vim
index 679bf3c..32ca967 100644
--- a/src/testdir/test_find_complete.vim
+++ b/src/testdir/test_find_complete.vim
@@ -15,22 +15,22 @@
 
   new
   set path=
-  call assert_fails('call feedkeys(":find\t\n", "xt")', 'E345:')
+  call assert_fails('call feedkeys(":find \t\n", "xt")', 'E471:')
   close
 
   new
   set path=.
-  call assert_fails('call feedkeys(":find\t\n", "xt")', 'E32:')
+  call assert_fails('call feedkeys(":find \t\n", "xt")', 'E471:')
   close
 
   new
   set path=.,,
-  call assert_fails('call feedkeys(":find\t\n", "xt")', 'E32:')
+  call assert_fails('call feedkeys(":find \t\n", "xt")', 'E471:')
   close
 
   new
   set path=./**
-  call assert_fails('call feedkeys(":find\t\n", "xt")', 'E32:')
+  call assert_fails('call feedkeys(":find \t\n", "xt")', 'E471:')
   close
 
   " We shouldn't find any file till this point
diff --git a/src/testdir/test_findfile.vim b/src/testdir/test_findfile.vim
index ac6d863..44c8982 100644
--- a/src/testdir/test_findfile.vim
+++ b/src/testdir/test_findfile.vim
@@ -222,4 +222,8 @@
   call CleanFiles()
   let &path = save_path
   close
+
+  call assert_fails('find', 'E471:')
+  call assert_fails('sfind', 'E471:')
+  call assert_fails('tabfind', 'E471:')
 endfunc