Fix reported crash (seg-fault) in smb_hashstr() due to previous commit

(calling strlen(NULL)).

src/smblib/smbhash.c

@@ -8,7 +8,7 @@
  * @format.tab-size 4		(Plain Text/Source Code File Header)			*
  * @format.use-tabs true	(see http://www.synchro.net/ptsc_hdr.html)		*
  *																			*
- * Copyright 2011 Rob Swindell - http://www.synchro.net/copyright.html		*
+ * Copyright 2012 Rob Swindell - http://www.synchro.net/copyright.html		*
  *																			*
  * This library is free software; you can redistribute it and/or			*
  * modify it under the terms of the GNU Lesser General Public License		*
@@ -232,10 +232,12 @@ hash_t* SMBCALL smb_hashstr(ulong msgnum, uint32_t t, unsigned source, unsigned
 		if(flags&SMB_HASH_LOWERCASE)
 			strlwr(p);
 	}
-	
-	hash=smb_hash(msgnum, t, source, flags, p?p:str, strlen(p));
 
-	FREE_AND_NULL(p);
+	if(p!=NULL) {
+		hash=smb_hash(msgnum, t, source, flags, p, strlen(p));
+		free(p);
+	} else
+		hash=smb_hash(msgnum, t, source, flags, str, strlen(str));
 
 	return(hash);
 }