prevent div by zero

src/FPS.cpp

@@ -25,7 +25,10 @@ void FPS::setUpdateInterval(int milli) {
 }
 
 void FPS::updateCurrent() {
-	current = framesSinceUpdate * 1000 * 1000 * 1000 / timeSinceUpdate.count();
+	if (timeSinceUpdate.count() == 0)
+		current = 0;
+	else
+		current = framesSinceUpdate * 1000 * 1000 * 1000 / (timeSinceUpdate.count());
 	framesSinceUpdate = 0;
 	timeSinceUpdate = nanoseconds(0);
 }