Fix #778, fix afterTransactionRunnable is called before popTo()

Author: YoKeyword

fragmentation_core/src/main/java/me/yokeyword/fragmentation/TransactionDelegate.java

@@ -238,12 +238,12 @@ void popTo(final String targetFragmentTag, final boolean includeTargetFragment,
             @Override
             public void run() {
                 doPopTo(targetFragmentTag, includeTargetFragment, afterPopTransactionRunnable, fm, popAnim);
+                
+                if (afterPopTransactionRunnable != null) {
+                    afterPopTransactionRunnable.run();
+                }
             }
         });
-
-        if (afterPopTransactionRunnable != null) {
-            afterPopTransactionRunnable.run();
-        }
     }
 
     /**