Update app.py

app.py

@@ -48,6 +48,8 @@ def get_seed(seed):
 def generate(input=DEFAULT_INPUT, filter_input="", negative_input=DEFAULT_NEGATIVE_INPUT, model=DEFAULT_MODEL, height=DEFAULT_HEIGHT, width=DEFAULT_WIDTH, steps=1, guidance=0, number=1, seed=None):
 
     repo = None
+    filter_input = filter_input || ""
+    negative_input = negative_input || DEFAULT_NEGATIVE_INPUT
     seed = get_seed(seed)
 
     print(input, filter_input, negative_input, model, height, width, steps, guidance, number, seed)