[gnome-builder] terminal: always set error string if shell discovery fails

[Christian Hergert <chergert src gnome org>]

commit f7238333c8879dbe6402db4d1a13f4b3a10e865a
Author: Christian Hergert <chergert redhat com>
Date:   Fri Sep 16 12:51:21 2016 -0700

    terminal: always set error string if shell discovery fails

 plugins/terminal/gb-terminal-view.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/plugins/terminal/gb-terminal-view.c b/plugins/terminal/gb-terminal-view.c
index 3aeaa9a..04d972d 100644
--- a/plugins/terminal/gb-terminal-view.c
+++ b/plugins/terminal/gb-terminal-view.c
@@ -117,6 +117,12 @@ gb_terminal_view_discover_shell (GCancellable  *cancellable,
         cached_shell = g_steal_pointer (&stdout_buf);
     }
 
+  if (cached_shell == NULL)
+    g_set_error_literal (error,
+                         G_IO_ERROR,
+                         G_IO_ERROR_FAILED,
+                         "Unknown error when discovering user shell");
+
   return cached_shell;
 }