Fix broken swagger documentation and requirements.txt parsing

Change-Id: If9932b9d3ca19f0e4d53dfcd03cd35fdacde8f62
diff --git a/lib/xos-genx/xosgenx/jinja2_extensions/base.py b/lib/xos-genx/xosgenx/jinja2_extensions/base.py
index f4929a9..7e10e7d 100644
--- a/lib/xos-genx/xosgenx/jinja2_extensions/base.py
+++ b/lib/xos-genx/xosgenx/jinja2_extensions/base.py
@@ -35,7 +35,7 @@
 
 
 def unquote(s):
-    if s.startswith('"') and s.endswith('"'):
+    if s and s.startswith('"') and s.endswith('"'):
         return s[1:-1]
     else:
         return s