Don't show the password reminder popup if the activity is finished

app/src/main/java/com/beemdevelopment/aegis/ui/AuthActivity.java

@@ -233,6 +233,10 @@ public class AuthActivity extends AegisActivity {
             popup.setElevation(5.0f);
         }
         _textPassword.post(() -> {
+            if (isFinishing()) {
+                return;
+            }
+
             // calculating the actual height of the popup window does not seem possible
             // adding 25dp seems to look good enough
             int yoff = _textPassword.getHeight()