[meld] Handle style theme not existing

[Kai Willadsen <kaiw src gnome org>]

commit 34d707c26683a922254c17f2156a0702d7829622
Author: Patrick Griffis <tingping tingping se>
Date:   Mon Oct 17 01:17:08 2016 -0400

    Handle style theme not existing

 meld/misc.py |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/meld/misc.py b/meld/misc.py
index 65d4d48..34057b5 100644
--- a/meld/misc.py
+++ b/meld/misc.py
@@ -187,7 +187,7 @@ def colour_lookup_with_fallback(name, attribute):
     from meld.settings import meldsettings
     source_style = meldsettings.style_scheme
 
-    style = source_style.get_style(name)
+    style = source_style.get_style(name) if source_style else None
     style_attr = getattr(style.props, attribute) if style else None
     if not style or not style_attr:
         base_style = get_base_style_scheme()