Base: fix conversion from Placement to Matrix

See also: https://forum.freecadweb.org/viewtopic.php?f=3&t=61000

src/Base/Rotation.cpp

@@ -172,10 +172,14 @@ void Rotation::getValue(Matrix4D & matrix) const
 {
     // Taken from <http://de.wikipedia.org/wiki/Quaternionen>
     //
-    const double x = this->quat[0];
-    const double y = this->quat[1];
-    const double z = this->quat[2];
-    const double w = this->quat[3];
+    const double l = sqrt(this->quat[0] * this->quat[0] +
+                          this->quat[1] * this->quat[1] +
+                          this->quat[2] * this->quat[2] +
+                          this->quat[3] * this->quat[3]);
+    const double x = this->quat[0] / l;
+    const double y = this->quat[1] / l;
+    const double z = this->quat[2] / l;
+    const double w = this->quat[3] / l;
 
     matrix[0][0] = 1.0-2.0*(y*y+z*z);
     matrix[0][1] = 2.0*(x*y-z*w);

src/Mod/Test/BaseTests.py

@@ -407,6 +407,24 @@ class MatrixTestCase(unittest.TestCase):
         res = self.mat * mat
         self.assertEqual(type(res), FreeCAD.Matrix)
 
+    def testMatrixPlacementMatrix(self):
+        # Example taken from https://forum.freecadweb.org/viewtopic.php?f=3&t=61000
+        mat = FreeCAD.Matrix(-0.470847778020266,
+                             0.8150598976807029,
+                             0.3376088628746235,
+                             -11.25290913640202,
+                             -0.8822144756796808,
+                             -0.4350066260577338,
+                             -0.180185641360483,
+                             -2876.45492562325,
+                             1.955470978815492e-9,
+                             -0.3826834326750831,
+                             0.923879538425552,
+                             941.3822018176414)
+        plm = FreeCAD.Placement(mat)
+        mat = plm.toMatrix()
+        self.assertEqual(mat.hasScale(), FreeCAD.ScaleType.NoScaling)
+
     def testAnything(self):
         with self.assertRaises(NotImplementedError):
             self.mat * "string"