MLBEDSW-2340: Make the tensor address default None

Signed-off-by: Charles Xu <charles.xu@arm.com>
Change-Id: I53d9d56acee57cff208dccb4822c1f1a461c416d
diff --git a/ethosu/vela/live_range.py b/ethosu/vela/live_range.py
index 8fe3d57..fe00b62 100644
--- a/ethosu/vela/live_range.py
+++ b/ethosu/vela/live_range.py
@@ -85,7 +85,7 @@
     def set_address(self, address):
         # Set address of all unaddressed tensors in LiveRange
         for tens in self.tensors:
-            if tens.address == 0:
+            if tens.address is None:
                 addr = address
             else:
                 # Limit to single tensor for the lr if the tensor address already assigned