fix wandering systems after edit to second or subsequent systems

WHen editing the second or later system on a page,
we don't relayout the previous systems on the page.
Thus, the already-spread value is used as a starting point
causing it to spread further and further with each edit,
and also the calculation of the restHeight for spread of systems
is also off.

Fix is to called the new restoreLayout2() for all those initial systems.

libmscore/layout.cpp

@@ -4618,22 +4618,29 @@ void LayoutContext::collectPage()
       {
       const qreal slb = score->styleP(Sid::staffLowerBorder);
       bool breakPages = score->layoutMode() != LayoutMode::SYSTEM;
-      //qreal y         = prevSystem ? prevSystem->y() + prevSystem->height() : page->tm();
       qreal ey        = page->height() - page->bm();
+      qreal y         = 0.0;
 
       System* nextSystem = 0;
       int systemIdx = -1;
 
-      qreal y = page->systems().isEmpty() ? page->tm() : page->system(0)->y() + page->system(0)->height();
       // re-calculate positions for systems before current
       // (they may have been filled on previous layout)
       int pSystems = page->systems().size();
+      if (pSystems > 0) {
+            page->system(0)->restoreLayout2();
+            y = page->system(0)->y() + page->system(0)->height();
+            }
+      else {
+             y = page->tm();
+            }
       for (int i = 1; i < pSystems; ++i) {
             System* cs = page->system(i);
             System* ps = page->system(i - 1);
             qreal distance = ps->minDistance(cs);
             y += distance;
             cs->setPos(page->lm(), y);
+            cs->restoreLayout2();
             y += cs->height();
             }