Undo broken on Rebase dashboard
After performing an action on the Rebase dashboard, hitting Super-Z doesn’t undo the action. It outputs the following error to the console:

```
Traceback (most recent call last):
  File "/Users/kyank/Library/Application Support/Sublime Text 3/Packages/GitSavvy/core/interfaces/rebase.py", line 353, in run_async
    branch_name, ref = self.interface.get_branch_state()
ValueError: too many values to unpack (expected 2)
```

Reproduced on latest release and master.

diff --git a/core/interfaces/rebase.py b/core/interfaces/rebase.py
index 9b7da80e..25b74d30 100644
--- a/core/interfaces/rebase.py
+++ b/core/interfaces/rebase.py
@@ -350,7 +350,7 @@ class GsRebaseUndoCommand(TextCommand, GitCommand):
         if log is None or cursor is None or cursor == -1:
             return
 
-        branch_name, ref = self.interface.get_branch_state()
+        branch_name, ref, _ = self.interface.get_branch_state()
 
         current = log[cursor]
         if current["branch_name"] != branch_name:
@@ -388,7 +388,7 @@ class GsRebaseRedoCommand(TextCommand, GitCommand):
         if log is None or cursor is None or cursor == len(log) - 1:
             return
 
-        branch_name, ref = self.interface.get_branch_state()
+        branch_name, ref, _ = self.interface.get_branch_state()
 
         undone_action = log[cursor+1]
         if undone_action["branch_name"] != branch_name:
['core/interfaces/rebase.py']