Correct inital loading of BorderActivate

Summary:
We have a comma separated list:

"".split(',') returns ""
JS decides that's worth itterating over, and we implicitly cast "" to a
number which means we register on screen edge 0 (the top).

We can't use typeof or isFinite because valid entries are still strings
at this point.

Test Plan:
Ran with default config, no longer registered on top edge
Set an edge properly in the KCM. Still worked.

Reviewers: #plasma, mart

Reviewed By: mart

Subscribers: mart, plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D4113

scripts/minimizeall/contents/code/main.js

@@ -59,8 +59,11 @@ function init() {
 
     var borders = readConfig("BorderActivate", "").toString().split(",");
     for (var i in borders) {
-        registeredBorders.push(borders[i]);
-        registerScreenEdge(borders[i], minimizeAllWindows);
+        var border = borders[i];
+        if (border != "") {
+            registeredBorders.push(border);
+            registerScreenEdge(border, minimizeAllWindows);
+        }
     }
 }