Don't bomb if original didn't exist (#2295)

If we don't have an existing file, original ends up as None.  Bug
introduced in 70fa125

files/blockinfile.py

@@ -281,7 +281,7 @@ def main():
 
     if lines:
         result = '\n'.join(lines)
-        if original.endswith('\n'):
+        if original and original.endswith('\n'):
             result += '\n'
     else:
         result = ''