[gimp] fix a few potential use-before-check errors

[Simon Budig <simon src gnome org>]

commit 7928be2255ae84c81b7762a53b63a9562cf75449
Author: Simon Budig <simon budig de>
Date:   Sat Aug 16 00:29:16 2014 +0200

    fix a few potential use-before-check errors
    
    Spotted by Andrey Karpov using static code analysis:
       http://www.viva64.com/en/b/0273/

 plug-ins/common/sample-colorize.c |    2 +-
 plug-ins/file-psd/psd-load.c      |    3 +--
 plug-ins/imagemap/imap_object.c   |    4 +++-
 3 files changed, 5 insertions(+), 4 deletions(-)
---
diff --git a/plug-ins/common/sample-colorize.c b/plug-ins/common/sample-colorize.c
index 8aa4281..f4310a1 100644
--- a/plug-ins/common/sample-colorize.c
+++ b/plug-ins/common/sample-colorize.c
@@ -893,7 +893,7 @@ update_preview (gint32 *id_ptr)
 
   if (g_Sdebug)
     printf ("UPD PREVIEWS   ID:%d ENABLE_UPD:%d\n",
-            (int)*id_ptr, (int)g_di.enable_preview_update);
+            id_ptr ? (int) *id_ptr : -1, (int)g_di.enable_preview_update);
 
   if (id_ptr == NULL || !g_di.enable_preview_update)
     return;
diff --git a/plug-ins/file-psd/psd-load.c b/plug-ins/file-psd/psd-load.c
index ee82be1..373608d 100644
--- a/plug-ins/file-psd/psd-load.c
+++ b/plug-ins/file-psd/psd-load.c
@@ -1505,8 +1505,7 @@ add_layers (gint32     image_id,
                       gimp_layer_set_apply_mask (layer_id,
                                                  ! lyr_a[lidx]->layer_mask.mask_flags.disabled);
                     }
-                  if (pixels)
-                    g_free (pixels);
+                  g_free (pixels);
                 }
             }
           for (cidx = 0; cidx < lyr_a[lidx]->num_channels; ++cidx)
diff --git a/plug-ins/imagemap/imap_object.c b/plug-ins/imagemap/imap_object.c
index 786dc02..65a4653 100644
--- a/plug-ins/imagemap/imap_object.c
+++ b/plug-ins/imagemap/imap_object.c
@@ -533,9 +533,11 @@ ObjectList_t*
 object_list_append_list(ObjectList_t *des, ObjectList_t *src)
 {
    GList *p;
+   if (!src)
+     return des;
    for (p = src->list; p; p = p->next)
       object_list_append(des, object_clone((Object_t*) p->data));
-   object_list_set_changed(des, (src) ? TRUE : FALSE);
+   object_list_set_changed(des, TRUE);
    return des;
 }