[gnome-software] plugin loader: Fix a crash in gs_plugin_loader_helper_free

[Kalev Lember <klember src gnome org>]

commit 0c0e6b22047c174099e4f9b89a439968d4e50078
Author: Kalev Lember <klember redhat com>
Date:   Wed Jan 10 13:44:53 2018 +0100

    plugin loader: Fix a crash in gs_plugin_loader_helper_free
    
    Don't unconditionally dereference an app associated with a plugin job,
    without checking first that it's non-NULL.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1515467

 lib/gs-plugin-loader.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/lib/gs-plugin-loader.c b/lib/gs-plugin-loader.c
index 7247090..d5cb758 100644
--- a/lib/gs-plugin-loader.c
+++ b/lib/gs-plugin-loader.c
@@ -210,7 +210,11 @@ gs_plugin_loader_helper_free (GsPluginLoaderHelper *helper)
        case GS_PLUGIN_ACTION_INSTALL:
        case GS_PLUGIN_ACTION_REMOVE:
        case GS_PLUGIN_ACTION_UPDATE:
-               gs_app_set_progress (gs_plugin_job_get_app (helper->plugin_job), 0);
+               {
+                       GsApp *app = gs_plugin_job_get_app (helper->plugin_job);
+                       if (app != NULL)
+                               gs_app_set_progress (app, 0);
+               }
                break;
        default:
                break;