Fix 'getViewVector' returning inverted vector

Despite the wrong value, this change is harmless since the direction of
the vector is not really required.

source/blender/editors/transform/transform_generics.c

@@ -69,7 +69,7 @@
 void getViewVector(const TransInfo *t, const float coord[3], float vec[3])
 {
   if (t->persp != RV3D_ORTHO) {
-    sub_v3_v3v3(vec, coord, t->viewinv[3]);
+    sub_v3_v3v3(vec, t->viewinv[3], coord);
   }
   else {
     copy_v3_v3(vec, t->viewinv[2]);