[gimp] app: fix warnings in GimpTileHandlerIscissors

[Michael Natterer <mitch src gnome org>]

commit aa3cb40600cad2f8aa3edc6ad87cd61b2ca89e55
Author: Michael Natterer <mitch gimp org>
Date:   Mon Mar 30 22:51:13 2015 +0200

    app: fix warnings in GimpTileHandlerIscissors

 app/tools/gimptilehandleriscissors.c |   24 +++++++++++++-----------
 1 files changed, 13 insertions(+), 11 deletions(-)
---
diff --git a/app/tools/gimptilehandleriscissors.c b/app/tools/gimptilehandleriscissors.c
index dd4150d..13820ee 100644
--- a/app/tools/gimptilehandleriscissors.c
+++ b/app/tools/gimptilehandleriscissors.c
@@ -235,17 +235,19 @@ gimp_tile_handler_iscissors_validate (GimpTileHandlerValidate *validate,
                       temp2, GEGL_RECTANGLE (0, 0, rect->width, rect->height),
                       vert_deriv, 3, 1, GIMP_NEGATIVE_CONVOL, FALSE);
 
-  maxgrad_conv1 = gegl_buffer_linear_open (temp1,
-                                           GEGL_RECTANGLE (0, 0,
-                                                           rect->width,
-                                                           rect->height),
-                                           &stride1, NULL);
-
-  maxgrad_conv2 = gegl_buffer_linear_open (temp2,
-                                           GEGL_RECTANGLE (0, 0,
-                                                           rect->width,
-                                                           rect->height),
-                                           &stride2, NULL);
+  maxgrad_conv1 =
+    (guchar *) gegl_buffer_linear_open (temp1,
+                                        GEGL_RECTANGLE (0, 0,
+                                                        rect->width,
+                                                        rect->height),
+                                        &stride1, NULL);
+
+  maxgrad_conv2 =
+    (guchar *) gegl_buffer_linear_open (temp2,
+                                        GEGL_RECTANGLE (0, 0,
+                                                        rect->width,
+                                                        rect->height),
+                                        &stride2, NULL);
 
   /* calculate overall gradient */