[xml-fold addon] Handle line-broken opening tags better

No longer creates a fold spot for both lines of a line-broken
tag.

Closes #5179

addon/fold/xml-fold.js

@@ -138,7 +138,7 @@
     var iter = new Iter(cm, start.line, 0);
     for (;;) {
       var openTag = toNextTag(iter), end;
-      if (!openTag || iter.line != start.line || !(end = toTagEnd(iter))) return;
+      if (!openTag || !(end = toTagEnd(iter)) || iter.line != start.line) return;
       if (!openTag[1] && end != "selfClose") {
         var startPos = Pos(iter.line, iter.ch);
         var endPos = findMatchingClose(iter, openTag[2]);