bux fix for single segment pendula

src/Pendulum.cpp

@@ -71,11 +71,10 @@ void Pendulum::update(double h, double g) {
 		if (i > 0){
 			V[i - 1] = (p1 - X[i - 1]) / h;
 			X[i - 1] = p1;
-
-			if (i == X.size() - 1){
-				V[i] = (p2 - X[i]) / h;
-				X[i] = p2;
-			}
+		}
+		if (i == X.size() - 1){
+			V[i] = (p2 - X[i]) / h;
+			X[i] = p2;
 		}
 
 		p1 = p2;