fix an error that happens when you send an empty image from txt2img to img2img

modules/generation_parameters_copypaste.py

@@ -37,6 +37,9 @@ def quote(text):
 
 
 def image_from_url_text(filedata):
+    if filedata is None:
+        return None
+
     if type(filedata) == list and len(filedata) > 0 and type(filedata[0]) == dict and filedata[0].get("is_file", False):
         filedata = filedata[0]