Added dialog for selecting a new stylesheet if the one from a set is not found;

'availible' is not a word

git-svn-id: svn://svn.code.sf.net/p/magicseteditor/code/trunk@657 0fc631ac-6414-0410-93d0-97cfa31319b6

src/util/io/package.cpp

@@ -82,7 +82,7 @@ void Package::open(const String& n) {
 	} else if (wxFileExists(filename)) {
 		openZipfile();
 	} else {
-		throw PackageError(_("Package not found: '") + filename + _("'"));
+		throw PackageNotFoundError(_("Package not found: '") + filename + _("'"));
 	}
 }