Fix crash in custom cell renderer size methods

clients/ovcc-gtk/src/ovccgtk-cell-renderer-color.c

@@ -193,9 +193,17 @@ ovccgtk_cell_renderer_color_get_preferred_width (GtkCellRenderer    *cell,
 {
   OVCCGtkCellRendererColor *self = OVCCGTK_CELL_RENDERER_COLOR (cell);
   gint                      xpad;
+  gint                      width;
   
   gtk_cell_renderer_get_padding (cell, &xpad, NULL);
-  *minimum_width = *natural_width = xpad * 2 + self->priv->size;
+  width = xpad * 2 + self->priv->size;
+  
+  if (minimum_width) {
+    *minimum_width = width;
+  }
+  if (natural_width) {
+    *natural_width = width;
+  }
 }
 
 static void
@@ -206,9 +214,17 @@ ovccgtk_cell_renderer_color_get_preferred_height (GtkCellRenderer    *cell,
 {
   OVCCGtkCellRendererColor *self = OVCCGTK_CELL_RENDERER_COLOR (cell);
   gint                      ypad;
+  gint                      height;
   
   gtk_cell_renderer_get_padding (cell, NULL, &ypad);
-  *minimum_height = *natural_height = ypad * 2 + self->priv->size;
+  height = ypad * 2 + self->priv->size;
+  
+  if (minimum_height) {
+    *minimum_height = height;
+  }
+  if (natural_height) {
+    *natural_height = height;
+  }
 }
 
 static void