QQuaternion: fix qFuzzyCompare() precondition violation

qFuzzyCompare() requires that neither argument is numerically
zero. One user of this function cannot guarantee this, because, while
they check for zero, they do so _after_ calling qFuzzyCompare() with
that value, so the check comes too late.

Fix by swapping the two checks around (so we check for == 0 before we
check for == 1).

Amends 8c1532e, which changed from
qFuzzyIsNull(x - 1) (which doesn't have the problem) to
qFuzzyCompare(x, 1) (which does).

Pick-to: 6.8 6.5
Task-number: QTBUG-142020
Change-Id: I054449b5510217f83479c5a028986c569f54084c
Reviewed-by: Ivan Solovev <[email protected]>
Reviewed-by: Edward Welbourne <[email protected]>
(cherry picked from commit e6f5161)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

Author: marcmutz

src/gui/math3d/qquaternion.cpp

@@ -409,7 +409,7 @@ QQuaternion QQuaternion::fromAxisAndAngle
         (float x, float y, float z, float angle)
 {
     float length = qHypot(x, y, z);
-    if (!qFuzzyCompare(length, 1.0f) && !qFuzzyIsNull(length)) {
+    if (!qFuzzyIsNull(length) && !qFuzzyCompare(length, 1.0f)) {
         x /= length;
         y /= length;
         z /= length;