Bugfix: crash on exit

This crash started to happen with the bugfix
for the black-on-black tree expander icon.
It was caused by the styling that was attached
to the widgets in order to fix this. Apparently
Qt does not like to attach proxy styles dyna-
mically.

Now, the styling is applied globally and this
issue is fixed.

src/laybasic/laybasic.pro

@@ -67,7 +67,6 @@ FORMS = \
   SaveLayoutOptionsDialog.ui \
   SaveLayoutAsOptionsDialog.ui \
   SelectStippleForm.ui \
-  SimpleCellSelectionForm.ui \
   TipDialog.ui \
   UserPropertiesForm.ui \
   UserPropertiesEditForm.ui \
@@ -176,7 +175,8 @@ SOURCES = \
     laySelectLineStyleForm.cc \
     layLineStylePalette.cc \
     layEditLineStylesForm.cc \
-    layEditLineStyleWidget.cc
+    layEditLineStyleWidget.cc \
+    layBackgroundAwareTreeStyle.cc
 
 HEADERS = \
   gtf.h \
@@ -270,7 +270,8 @@ HEADERS = \
     layEditLineStylesForm.h \
     layEditLineStyleWidget.h \
     laybasicCommon.h \
-    laybasicConfig.h
+    laybasicConfig.h \
+    layBackgroundAwareTreeStyle.h
 
 INCLUDEPATH += ../tl ../gsi ../db ../rdb
 DEPENDPATH += ../tl ../gsi ../db ../rdb