feat: Refactor app.py to handle trigger word and style prompt

app.py

@@ -58,11 +58,11 @@ def infer(selected_index, prompt, style_prompt, inf_steps, guidance_scale, width
         )
         weight_name = result.result()[2]['value']
 
-        if prompt.startswith(trigger_word):
-            prompt = prompt[len(trigger_word):]
+        if trigger_word and prompt.startswith(trigger_word):
+            prompt = prompt[len(trigger_word):].lstrip()
 
-        if prompt.endswith(style_prompt):
-            prompt = prompt[:-len(style_prompt)]
+        if style_prompt and prompt.startswith(style_prompt):
+            prompt = prompt[len(style_prompt):].lstrip()
         
         prompt_arr = [trigger_word, prompt, style_prompt]
         prompt = '. '.join([element.strip() for element in prompt_arr if element.strip() != ''])