ClearTo with first and last index doesn't handle a single pixel

The argument valid test needed to support that first and last could be
the same

library.json

@@ -8,7 +8,7 @@
     "type": "git",
     "url": "https://github.com/Makuna/NeoPixelBus"
   },
-  "version": "2.2.2",
+  "version": "2.2.3",
   "frameworks": "arduino",
   "platforms": "*"
 }