Fix lib update crashing when no libs are installed (resolve issue #19)

platformio/commands/lib.py

@@ -140,9 +140,12 @@ def lib_show(name):
 @cli.command("update", short_help="Update installed libraries")
 def lib_update():
     lm = LibraryManager(get_lib_dir())
-    lib_names = lm.get_installed()
-    versions = get_api_result("/lib/version/" + ",".join(lib_names))
 
+    lib_names = lm.get_installed()
+    if not lib_names:
+        return
+
+    versions = get_api_result("/lib/version/" + ",".join(lib_names))
     for name in lib_names:
         info = lm.get_info(name)
 

platformio/libmanager.py

@@ -33,6 +33,8 @@ class LibraryManager(object):
 
     def get_installed(self):
         items = []
+        if not isdir(self.lib_dir):
+            return items
         for item in listdir(self.lib_dir):
             conf_path = join(self.lib_dir, item, self.CONFIG_NAME)
             if isfile(conf_path):