fix(infinite-scroll): load more data if needed

detect if more data needs to be loaded after the initial load. Before if
not enough data was loaded to enable scrolling, no more data would be
loaded. Resolves issue
[4363](#4363)

Author: DmitryEfimenko

src/features/infinite-scroll/js/infinite-scroll.js

@@ -368,6 +368,12 @@
 
           newVisibleRows = grid.getVisibleRowCount();
 
+          // in case not enough data is loaded to enable scroller - load more data
+          var canvasHeight = rowHeight * newVisibleRows;
+          if (grid.infiniteScroll.scrollDown && (viewportHeight > canvasHeight)) {
+            grid.api.infiniteScroll.raise.needLoadMoreData();
+          }
+
           if ( grid.infiniteScroll.direction === uiGridConstants.scrollDirection.UP ){
             oldTop = grid.infiniteScroll.prevScrollTop || 0;
             newTop = oldTop + (newVisibleRows - grid.infiniteScroll.previousVisibleRows)*rowHeight;