Refresh the tree only if it is not busy.

Although the tree may become busy after the check and before refresh, the check avoids the "Ignored reentrant call exception" in practice.

Fixed #64.

Author: reprogrammer

plugins/checker.framework.errorcentric.view/src/checker/framework/errorcentric/view/views/ErrorCentricView.java

@@ -330,7 +330,9 @@ public void setFocus() {
     public void update(final TreeObject node) {
         Display.getDefault().syncExec(new Runnable() {
             public void run() {
-                viewer.refresh();
+                if (!viewer.isBusy()) {
+                    viewer.refresh();
+                }
             }
         });
     }