minor fixes

gui/qt/main_window.py

@@ -980,6 +980,8 @@ class ElectrumWindow(QMainWindow):
         self.payment_request = None
 
     def pay_from_URI(self,URI):
+        if not URI:
+            return
         address, amount, label, message, request_url = util.parse_URI(URI)
         try:
             address, amount, label, message, request_url = util.parse_URI(URI)

lib/util.py

@@ -163,7 +163,7 @@ def parse_URI(uri):
     from decimal import Decimal
 
     if ':' not in uri:
-        assert bitcoin.is_address(url)
+        assert bitcoin.is_address(uri)
         return uri, None, None, None, None
 
     u = urlparse.urlparse(uri)