[evolution] Fix some potential null pointer dereferences.

[Matthew Barnes <mbarnes src gnome org>]

commit 73716c500bc2f9dd2c0057b3d57ccc340d5e1017
Author: Matthew Barnes <mbarnes redhat com>
Date:   Fri Jan 15 22:19:49 2010 -0500

    Fix some potential null pointer dereferences.
    
    Caught by the Clang Static Analyzer.

 modules/calendar/e-cal-shell-backend.c  |    6 ++++--
 modules/calendar/e-memo-shell-backend.c |    6 ++++--
 modules/calendar/e-task-shell-backend.c |    6 ++++--
 3 files changed, 12 insertions(+), 6 deletions(-)
---
diff --git a/modules/calendar/e-cal-shell-backend.c b/modules/calendar/e-cal-shell-backend.c
index bf6f2e1..232e846 100644
--- a/modules/calendar/e-cal-shell-backend.c
+++ b/modules/calendar/e-cal-shell-backend.c
@@ -600,9 +600,11 @@ cal_shell_backend_handle_uri_cb (EShellBackend *shell_backend,
 
 	client = auth_new_cal_from_source (source, source_type);
 	if (client == NULL || !e_cal_open (client, TRUE, &error)) {
-		g_printerr ("%s\n", error->message);
+		if (error != NULL) {
+			g_printerr ("%s\n", error->message);
+			g_error_free (error);
+		}
 		g_object_unref (source_list);
-		g_error_free (error);
 		goto exit;
 	}
 
diff --git a/modules/calendar/e-memo-shell-backend.c b/modules/calendar/e-memo-shell-backend.c
index 067613e..10a1ea9 100644
--- a/modules/calendar/e-memo-shell-backend.c
+++ b/modules/calendar/e-memo-shell-backend.c
@@ -426,9 +426,11 @@ memo_shell_backend_handle_uri_cb (EShellBackend *shell_backend,
 
 	client = auth_new_cal_from_source (source, source_type);
 	if (client == NULL || !e_cal_open (client, TRUE, &error)) {
-		g_printerr ("%s\n", error->message);
+		if (error != NULL) {
+			g_printerr ("%s\n", error->message);
+			g_error_free (error);
+		}
 		g_object_unref (source_list);
-		g_error_free (error);
 		goto exit;
 	}
 
diff --git a/modules/calendar/e-task-shell-backend.c b/modules/calendar/e-task-shell-backend.c
index d20a359..1a8bee5 100644
--- a/modules/calendar/e-task-shell-backend.c
+++ b/modules/calendar/e-task-shell-backend.c
@@ -431,9 +431,11 @@ task_shell_backend_handle_uri_cb (EShellBackend *shell_backend,
 
 	client = auth_new_cal_from_source (source, source_type);
 	if (client == NULL || !e_cal_open (client, TRUE, &error)) {
-		g_printerr ("%s\n", error->message);
+		if (error != NULL) {
+			g_printerr ("%s\n", error->message);
+			g_error_free (error);
+		}
 		g_object_unref (source_list);
-		g_error_free (error);
 		goto exit;
 	}