fix for quaternion::toAngleAxis, angle was QNaN when W < -1

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@758 dfc29bdd-3216-0410-991c-e03cc46cb475

include/quaternion.h

@@ -473,7 +473,7 @@ inline void quaternion::toAngleAxis(f32 &angle, core::vector3df &axis) const
 {
 	f32 scale = sqrt (X*X + Y*Y + Z*Z);
 
-	if (core::equals(scale,0.0f) || W > 1.0f)
+	if (core::equals(scale,0.0f) || W > 1.0f || W < -1.0f)
 	{
 		angle = 0.0f;
 		axis.X = 0.0f;