Regression with qbs.architecture behavior

With Qbs 1.9.0, the behavior Qbs has changed significantly regarding code that queries qbs.architecture. Two regressions can be observed:

1. In Qbs 1.9.0, qbs.architecture is undefined on project level. This wasn't the case in Qbs 1.8.1 and earlier.
2. On product level, depending on qbs.architecture has different results in Qbs 1.9.0 than in Qbs 1.8.1 and earlier.