Allow non-loaded pins to be removed

Closes #80

Clover/app/src/main/java/org/floens/chan/core/presenter/ThreadPresenter.java

@@ -136,15 +136,15 @@ public class ThreadPresenter implements ChanLoader.ChanLoaderCallback, PostAdapt
     }
 
     public boolean pin() {
-        if (chanLoader.getThread() != null) {
         Pin pin = watchManager.findPinByLoadable(loadable);
         if (pin == null) {
+            if (chanLoader.getThread() != null) {
                 Post op = chanLoader.getThread().op;
                 watchManager.addPin(loadable, op);
+            }
         } else {
             watchManager.removePin(pin);
         }
-        }
         return isPinned();
     }