minor code cleaning

DEVSIX-1267

Author: pavel-morozov-duallab

layout/src/main/java/com/itextpdf/layout/margincollapse/MarginsCollapseHandler.java

@@ -240,9 +240,6 @@ public void endMarginsCollapse(Rectangle layoutBox) {
         boolean lastChildMarginJoinedToParent = prevChildMarginInfo != null && prevChildMarginInfo.isIgnoreOwnMarginBottom() && !lastKidCollapsedAfterHasClearanceApplied;
         if (lastChildMarginJoinedToParent) {
             ownCollapseAfter = prevChildMarginInfo.getOwnCollapseAfter();
-            if (ownCollapseAfter == null) {
-                ownCollapseAfter = new MarginsCollapse();
-            }
         } else {
             ownCollapseAfter = new MarginsCollapse();
         }