plotting bug fix

app.py

@@ -185,7 +185,7 @@ class ArxivSearch:
                 marker=dict(size=3.5, color='orange', opacity=0.75),
                 name='Results'
             )
-            if self.query_encoding is not None and self.query_encoding.shape[0] > 0:
+            if query_point.shape[0] > 0:
                 query_trace = go.Scatter3d(
                     x=query_point[:, 0],
                     y=query_point[:, 1],