Minor change

oargen.py

@@ -50,9 +50,9 @@ def main():
     command = ["oarsub"]
     properties = "-p \""
     if args.gpu:
-        properties += "gpu IS NOT NULL"
+        properties += "(gpu IS NOT NULL)"
     else:
-        properties += "gpu IS NULL"
+        properties += "(gpu IS NULL)"
     if args.host is not None:
         properties += " AND host LIKE '{}'".format(args.host)
     properties += "\""