app: use the GParamSpec's nick as label in gimp_prop_spin_scale_new()

if a NULL label was passed. Override this with explicit calls to
gimp_spin_scale_set_label() in the two cases where we really don't
want a label.

app/tools/gimpcolorbalancetool.c

@@ -168,6 +168,7 @@ create_levels_scale (GObject     *config,
 
   scale = gimp_prop_spin_scale_new (config, property_name,
                                     NULL, 0.01, 0.1, 0);
+  gimp_spin_scale_set_label (GIMP_SPIN_SCALE (scale), NULL);
   gimp_prop_widget_set_factor (scale, 100.0, 0.0, 0.0, 1);
   gtk_table_attach_defaults (GTK_TABLE (table), scale, 1, 2, col, col + 1);
   gtk_widget_show (scale);

app/tools/gimptransformoptions.c

@@ -31,6 +31,7 @@
 #include "core/gimptoolinfo.h"
 
 #include "widgets/gimppropwidgets.h"
+#include "widgets/gimpspinscale.h"
 #include "widgets/gimpwidgets-utils.h"
 
 #include "gimprotatetool.h"
@@ -438,6 +439,7 @@ gimp_transform_options_gui (GimpToolOptions *tool_options)
   /*  the grid density scale  */
   scale = gimp_prop_spin_scale_new (config, "grid-size", NULL,
                                     1.8, 8.0, 0);
+  gimp_spin_scale_set_label (GIMP_SPIN_SCALE (scale), NULL);
   gtk_container_add (GTK_CONTAINER (frame), scale);
 
   g_object_bind_property_full (config, "grid-type",

app/widgets/gimppropwidgets.c

@@ -497,6 +497,9 @@ gimp_prop_spin_scale_new (GObject     *config,
   if (! G_IS_PARAM_SPEC_DOUBLE (param_spec))
     digits = 0;
 
+  if (! label)
+    label = g_param_spec_get_nick (param_spec);
+
   adjustment = gtk_adjustment_new (value, lower, upper,
                                    step_increment, page_increment, 0.0);