make input handling more robust

app.py

@@ -60,7 +60,13 @@ coexp_score_threshold = 0.85
 # Parse and check the user input #
 ##################################
 
-seed_gene_ids = [gene_id.strip() for gene_id in input_gene_ids.split("\n")]
+seed_genes = []
+for input_gene_id in input_gene_ids.split("\n"):
+    gene_id = input_gene_id.strip()
+    if gene_id == "":
+        continue
+    else:
+        seed_genes.append(gene_id)
 
 neighbors = []
 for seed_gene_id in seed_gene_ids: