[gedit-code-assistance] Fix crash when closing several documents

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 7c562e35d952b42febd4c76fa9ef7ba872d56788
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Thu Mar 19 16:57:22 2015 +0100

    Fix crash when closing several documents

 src/gca-backend.vala |   23 +++++++++++++++++++----
 1 files changed, 19 insertions(+), 4 deletions(-)
---
diff --git a/src/gca-backend.vala b/src/gca-backend.vala
index 5254754..64862e5 100644
--- a/src/gca-backend.vala
+++ b/src/gca-backend.vala
@@ -197,8 +197,16 @@ class Backend : Object
        {
                unsaved_document.begin(view, (obj, res) => {
                        var data_path = unsaved_document.end(res);
-                       var path = view.document.path;
-                       var cursor = view.document.cursor;
+
+                       var doc = view.document;
+                       if (doc == null) {
+                               // This happens when a document has been closed while we're
+                               // getting the unsaved document
+                               return;
+                       }
+
+                       var path = doc.path;
+                       var cursor = doc.cursor;
 
                        var options = new HashTable<string, Variant>(str_hash, str_equal);
 
@@ -235,8 +243,15 @@ class Backend : Object
                open_documents.begin(view, (obj, res) => {
                        var docs = open_documents.end(res);
 
-                       var path = view.document.path;
-                       var cursor = view.document.cursor;
+                       var doc = view.document;
+                       if (doc == null) {
+                               // This happens when a document has been closed while we're
+                               // opening the documents
+                               return;
+                       }
+
+                       var path = doc.path;
+                       var cursor = doc.cursor;
 
                        var options = new HashTable<string, Variant>(str_hash, str_equal);