patch 8.0.0602: when gF fails to edit the file the cursor still moves

Problem:    When gF fails to edit the file the cursor still moves to the found
            line number.
Solution:   Check the return value of do_ecmd(). (Michael Hwang)
diff --git a/src/testdir/test_gf.vim b/src/testdir/test_gf.vim
index c4aa6f9..1f3db24 100644
--- a/src/testdir/test_gf.vim
+++ b/src/testdir/test_gf.vim
@@ -1,7 +1,7 @@
 
 " This is a test if a URL is recognized by "gf", with the cursor before and
 " after the "://".  Also test ":\\".
-function! Test_gf_url()
+func Test_gf_url()
   enew!
   call append(0, [
       \ "first test for URL://machine.name/tmp/vimtest2a and other text",
@@ -30,4 +30,25 @@
 
   set isf&vim
   enew!
-endfunction
+endfunc
+
+func Test_gF()
+  new
+  call setline(1, ['111', '222', '333', '444'])
+  w! Xfile
+  close
+  new
+  call setline(1, ['one', 'Xfile:3', 'three'])
+  2
+  call assert_fails('normal gF', 'E37:')
+  call assert_equal(2, getcurpos()[1])
+  w! Xfile2
+  normal gF
+  call assert_equal('Xfile', bufname('%'))
+  call assert_equal(3, getcurpos()[1])
+
+  call delete('Xfile')
+  call delete('Xfile2')
+  bwipe Xfile
+  bwipe Xfile2
+endfunc