fix loop scatter

app.py

@@ -201,7 +201,7 @@ def get_heatmap(celltype, gene, locus1, locus2, heatmap_range, heatmap_x, heatma
     #img = draw_heatmap(mat, 0, return_image=True)
     fig, ax = plt.subplots(figsize=(4, 4))
     ax.imshow(mat, cmap='Reds', norm=PowerNorm(gamma=0.3), interpolation=None)
-    if heatmap_x is not None and heatmap_y is not None:
+    if heatmap_x != '' and heatmap_y != '':
         ax.scatter(int(heatmap_x), int(heatmap_y), color='green', marker='*', s=100)
     # remove white padding
     plt.subplots_adjust(left=0, right=1, top=1, bottom=0)