Update pyang-apteryx-xml.py and pyang-cpaths.py

pyang-apteryx-xml.py was modified to allow features to be passed an
empty string. This helps certain script files.

pyang-cpaths.py was modified to fix an error noticed when compiling the
openconfig-interfaces model.

pyang-apteryx-xml.py

@@ -180,8 +180,10 @@ def emit(self, ctx, modules, fd):
         if rev is not None:
             root.set("version", rev.arg)
         if ctx.opts.features:
-            features_string = ','.join(ctx.opts.features)
-            root.set("features", features_string)
+            # Ignore the features list if it is empty
+            if len(ctx.opts.features[0]) > 0:
+                features_string = ','.join(ctx.opts.features)
+                root.set("features", features_string)
         if ctx.opts.deviations:
             lst = []
             for x in ctx.opts.deviations:

pyang-cpaths.py

@@ -131,7 +131,8 @@ def print_node(node, module, prefix, fd, ctx, level=0, strip=0):
         typedef.i_config = node.i_config
         if node.i_default is not None:
             typedef.i_default = node.i_default
-            typedef.i_default_str = node.i_default_str
+            if hasattr(node, "i_default_str"):
+                typedef.i_default_str = node.i_default_str
         typedef.keyword = node.keyword
         node = typedef
         ntype = node.search_one('type')