not installing icon themes

Hello,

i'd like to start stripping unneeded stuff when building for headless, 
starting from images.

I've tried with --with-theme="" but got the default themes instead. 
Would it be ok to change the meaning of "" to be none instead of default?

Then i've tried with this patch which compiles fine but gives an error 
at install time because the installer still looks for them. Some 
grepping of "theme" in solenv shows gb_ResTarget_DEFIMAGESLOCATION which 
used later in $(call gb_ResTarget_get_target,%) makes me think that at 
least an icon set is mandatory. Any hint on a sensible approach?

thanks in advance,
riccardo

diff --git a/postprocess/Module_postprocess.mk 
b/postprocess/Module_postprocess.mk
index 0716ae7..f926306 100644
--- a/postprocess/Module_postprocess.mk
+++ b/postprocess/Module_postprocess.mk
@@ -17,14 +17,19 @@ $(eval $(call gb_Module_Module,postprocess))

 $(eval $(call gb_Module_add_targets,postprocess,\
        CustomTarget_config \
-       CustomTarget_images \
        CustomTarget_registry \
        Package_config \
-       Package_images \
        Package_registry \
        Rdb_services \
 ))

+ifneq ($(ENABLE_HEADLESS),TRUE)
+$(eval $(call gb_Module_add_targets,postprocess,\
+       CustomTarget_images \
+       Package_images \
+))
+endif
+
 ifeq ($(WINDOWS_BUILD_SIGNING),TRUE)
 $(eval $(call gb_Module_add_targets,postprocess,\
        CustomTarget_signing \