patch 7.4.2225
Problem:    Crash when placing a sign in a deleted buffer.
Solution:   Check for missing buffer name. (Dominique Pelle). Add a test.
diff --git a/src/testdir/test_signs.vim b/src/testdir/test_signs.vim
index 79e6098..93cc62c 100644
--- a/src/testdir/test_signs.vim
+++ b/src/testdir/test_signs.vim
@@ -181,3 +181,15 @@
   call assert_fails('sign place 1 buffer=', 'E158:')
   call assert_fails('sign define Sign2 text=', 'E239:')
 endfunc
+
+func Test_sign_delete_buffer()
+  new
+  sign define Sign text=x
+  let bufnr = bufnr('%')
+  new
+  exe 'bd ' . bufnr
+  exe 'sign place 61 line=3 name=Sign buffer=' . bufnr
+  call assert_fails('sign jump 61 buffer=' . bufnr, 'E934:')
+  sign unplace 61
+  sign undefine Sign
+endfunc