Fix IOBe in actions with empty condition trees. Needs backporting to 0.5.5.

git-svn-id: http://svn.dmdirc.com/trunk@3033 00569f92-eb28-0410-84fd-f71c24880f

src/com/dmdirc/actions/Action.java

             }
         }
 
-        if (config.isFlatDomain(DOMAIN_CONDITIONTREE)) {
+        if (config.isFlatDomain(DOMAIN_CONDITIONTREE)
+                && config.getFlatDomain(DOMAIN_CONDITIONTREE).size() > 0) {
             conditionTree = ConditionTree.parseString(
                     config.getFlatDomain(DOMAIN_CONDITIONTREE).get(0));