jit: Initialize function::m_blocks in ctor

This resolves the problem reported here:
https://mail.gnu.org/archive/html/bug-gnu-emacs/2021-11/msg00606.html
https://bugzilla.opensuse.org/show_bug.cgi?id=1192951

gcc/jit/ChangeLog:

	* jit-playback.c (function): Initialize m_blocks vector.

gcc/jit/jit-playback.c

@@ -1484,7 +1484,8 @@ function (context *ctxt,
 : m_ctxt(ctxt),
   m_inner_fndecl (fndecl),
   m_inner_bind_expr (NULL),
-  m_kind (kind)
+  m_kind (kind),
+  m_blocks ()
 {
   if (m_kind != GCC_JIT_FUNCTION_IMPORTED)
     {