Cleanup: use braces in mathutils switch statements

Also move error checking before variable declarations.

source/blender/python/mathutils/mathutils_Quaternion.cc

@@ -109,10 +109,6 @@ static PyObject *Quaternion_vectorcall(PyObject *type,
                                        const size_t nargsf,
                                        PyObject *kwnames)
 {
-  double angle = 0.0f;
-  float quat[QUAT_SIZE];
-  unit_qt(quat);
-
   if (UNLIKELY(kwnames && PyDict_Size(kwnames))) {
     PyErr_SetString(PyExc_TypeError,
                     "mathutils.Quaternion(): "
@@ -120,10 +116,15 @@ static PyObject *Quaternion_vectorcall(PyObject *type,
     return nullptr;
   }
 
+  double angle = 0.0f;
+  float quat[QUAT_SIZE];
+  unit_qt(quat);
+
   const size_t nargs = PyVectorcall_NARGS(nargsf);
   switch (nargs) {
-    case 0:
+    case 0: {
       break;
+    }
     case 1: {
       const int size = mathutils_array_parse(
           quat, 3, QUAT_SIZE, args[0], "mathutils.Quaternion()");
@@ -950,22 +951,25 @@ static PyObject *Quaternion_richcmpr(PyObject *a, PyObject *b, int op)
   }
 
   switch (op) {
-    case Py_NE:
+    case Py_NE: {
       ok = !ok;
       ATTR_FALLTHROUGH;
-    case Py_EQ:
+    }
+    case Py_EQ: {
       res = ok ? Py_False : Py_True;
       break;
-
+    }
     case Py_LT:
     case Py_LE:
     case Py_GT:
-    case Py_GE:
+    case Py_GE: {
       res = Py_NotImplemented;
       break;
-    default:
+    }
+    default: {
       PyErr_BadArgument();
       return nullptr;
+    }
   }
 
   return Py_NewRef(res);