Bugfix #6565

Nice discovery by Ralf (cheleb): crasher with colorband, caused by NULL
pointer reading. It actually reveiled a weakness in code too, the
buttonswindow context was not set appropriate when buttons window had not
a header...

source/blender/blenkernel/intern/texture.c

@@ -292,7 +292,7 @@ int do_colorband(ColorBand *coba, float in, float out[4])
 	float fac, mfac, t[4];
 	int a;
 	
-	if(coba->tot==0) return 0;
+	if(coba==NULL || coba->tot==0) return 0;
 	
 	cbd1= coba->data;
 	if(coba->tot==1) {

source/blender/src/butspace.c

@@ -698,11 +698,16 @@ void redraw_test_buttons(Object *new)
 /* callback */
 void drawbutspace(ScrArea *sa, void *spacedata)
 {
+	ID *id, *idfrom;
 	SpaceButs *sbuts= sa->spacedata.first;
 	View2D *v2d= &sbuts->v2d;
 	float col[3];
 	int tab, align=0;
 	
+	/* context */
+	buttons_active_id(&id, &idfrom);
+	G.buts->lockpoin= id;
+	
 	myortho2(v2d->cur.xmin, v2d->cur.xmax, v2d->cur.ymin, v2d->cur.ymax);
 
 	BIF_GetThemeColor3fv(TH_BACK, col);