Fix #31 - Tooltip shown when cursor not over node

Caused when currentTooltip is null. findAncestor ends up returning null, which equals currentTooltip and prevents the clearTimeout call from properly preventing the tooltip from being shown.

src/tooltip.js

@@ -48,8 +48,9 @@ function onMouseover(node) {
 function onMouseout(node, event) {
     // http://stackoverflow.com/questions/4697758/prevent-onmouseout-when-hovering-child-element-of-the-parent-absolute-div-withou
     var e = event.toElement || event.relatedTarget;
-    if (e == node || findAncestor(e, 'qp-node') == node ||
-        e == currentTooltip || findAncestor(e, 'qp-tt') == currentTooltip) {
+    if (e == node ||
+        findAncestor(e, 'qp-node') == node ||
+        (currentTooltip != null && (e == currentTooltip || findAncestor(e, 'qp-tt') == currentTooltip))) {
         return;
     }
     window.clearTimeout(timeoutId);