Return an error before trying to create an index in an unwriteable dir.
Patch from mwtalbert.
Index: main/src/modules/swmodule.cpp
===================================================================
--- main.orig/src/modules/swmodule.cpp	2009-08-30 19:46:22.000000000 -0700
+++ main/src/modules/swmodule.cpp	2009-08-30 19:47:07.000000000 -0700
@@ -1026,7 +1026,9 @@
 	if ((ch != '/') && (ch != '\\'))
 		target.append('/');
 	target.append("lucene");
-	FileMgr::createParent(target+"/dummy");
+	int iswritable = FileMgr::createParent(target+"/dummy");
+	if (iswritable == -1)
+		return -1;
 
 	ramDir = new RAMDirectory();
 	coreWriter = new IndexWriter(ramDir, an, true);