HEAD: crash in lt_dlcaller_get_data

[Eric Blake]

In trying to convert m4 to use lt_dlcaller_[gs]et_data, I discovered a core 
dump if you call get before set.  Applying this as obvious (plus a reindent).

2007-09-05  Eric Blake  <address@hidden>

        * libltdl/ltdl.c (lt_dlcaller_get_data): Work even when no caller
        has set data.

Index: libltdl/ltdl.c
===================================================================
RCS file: /sources/libtool/libtool/libltdl/ltdl.c,v
retrieving revision 1.264
diff -u -p -b -r1.264 ltdl.c
--- libltdl/ltdl.c      4 Sep 2007 18:01:33 -0000       1.264
+++ libltdl/ltdl.c      5 Sep 2007 14:45:49 -0000
@@ -2296,6 +2296,7 @@ lt_dlcaller_get_data  (lt_dlinterface_id
   lt__handle *cur = (lt__handle *) handle;
 
   /* Locate the index of the element with a matching KEY.  */
+  if (cur->interface_data)
   {
     int i;
     for (i = 0; cur->interface_data[i].key; ++i)