Fixed EditSession.makeCylinder's mimimum height check

CHANGELOG.txt

@@ -13,6 +13,7 @@
  - Update for new events system
  - Fixed /scriptname.js and no-double-slash settings not working
  - Corrected usage message for maze.js
+ - Fixed mimimum height check for cylinder generation
 
 5.1.1:
  - Fixed some compatibility issues with SpoutPlugin

src/main/java/com/sk89q/worldedit/EditSession.java

@@ -2077,8 +2077,8 @@ public class EditSession {
             pos = pos.subtract(0, height, 0);
         }
 
-        if (pos.getBlockY() - height - 1 < 0) {
-            height = pos.getBlockY() + 1;
+        if (pos.getBlockY() < 0) {
+            pos = pos.setY(0);
         } else if (pos.getBlockY() + height - 1 > world.getMaxY()) {
             height = world.getMaxY() - pos.getBlockY() + 1;
         }