Fix a crash that occurred when MWI SMDI messages expired.

(closes issue #14561)
Reported by: cmoss28


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@198311 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_smdi.c

@@ -309,8 +309,10 @@ static inline void unref_msg(void *msg, enum smdi_message_type type)
 	switch (type) {
 	case SMDI_MWI:
 		ASTOBJ_UNREF(mwi_msg, ast_smdi_mwi_message_destroy);
+		break;
 	case SMDI_MD:
 		ASTOBJ_UNREF(md_msg, ast_smdi_md_message_destroy);
+		break;
 	}
 }