XY: minor bugfix

properly handle width=0 OR height=0

wled00/FX_2Dfcn.cpp

@@ -191,7 +191,8 @@ uint32_t WS2812FX::getPixelColorXY(uint16_t x, uint16_t y) {
 uint16_t /*IRAM_ATTR*/ Segment::XY(uint16_t x, uint16_t y) {
   uint16_t width  = virtualWidth();   // segment width in logical pixels
   uint16_t height = virtualHeight();  // segment height in logical pixels
-  if ((width == 0) || (height == 0)) return 0; // softhack007 avoid div/0
+  if (width == 0) return 0;           // softhack007 avoid div/0
+  if (height == 0) return (x%width);  // softhack007 avoid div/0
   return (x%width) + (y%height) * width;
 }