Apply suggestion to soitool/soi.py

soitool/soi.py

@@ -379,7 +379,8 @@ class SOI:
         if self.placement_strategy == "auto":
             self.reorganize_rectpack()
         elif self.placement_strategy == "manual":
-            return
+            # nothing to do
+            pass
         else:
             raise Exception(
                 "Unknown placement strategy: {}".format(