[epiphany] window: Fix regression from the tab close rework

[Michael Catanzaro <mcatanzaro src gnome org>]

commit e88860e46ae7fde72fced9bc3bbde37657dff048
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Sun Feb 3 20:07:32 2019 -0600

    window: Fix regression from the tab close rework
    
    If data->id == 0 then it's not a valid source and we shouldn't try to
    remove it.

 src/ephy-window.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/ephy-window.c b/src/ephy-window.c
index 5d7bb72e8..b3893bf31 100644
--- a/src/ephy-window.c
+++ b/src/ephy-window.c
@@ -2774,8 +2774,10 @@ tab_has_modified_forms_cb (EphyWebView             *view,
 
   has_modified_forms = ephy_web_view_has_modified_forms_finish (view, result, NULL);
 
-  /* Cancel timer so it doesn't close while waiting for the user. */
-  g_source_remove (data->id);
+  if (data->id != 0) {
+    /* Ensure tab doesn't close while waiting for the user. */
+    g_source_remove (data->id);
+  }
 
   if (data->id != 0 &&
       data->window != NULL &&