Fixed error message for setImage

Former-commit-id: db0c38d865463048c6bb039c173e02ea685ae36e

libsrc/effectengine/Effect.cpp

@@ -270,7 +270,7 @@ PyObject* Effect::wrapSetImage(PyObject *self, PyObject *args)
 			}
 			else
 			{
-				PyErr_SetString(PyExc_RuntimeError, "Length of bytearray argument should be 3*ledCount");
+				PyErr_SetString(PyExc_RuntimeError, "Length of bytearray argument should be 3*width*height");
 				return nullptr;
 			}
 		}