fix environment of JS Process
fix environment of JS Process

The environment of the JS class Process is empty if the build environment
has not been initialized yet. This can happen if one uses Process on the
RHS of a binding like Group.name.

Task-number: QBS-547
Change-Id: I1341c8dbbc677adcc3e3f5842a95d6f8aeebf09b
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@digia.com>

Distrotech/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,gatzka/qt-labs-qbs,gatzka/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,villytiger/qbs,gatzka/qt-labs-qbs,Distrotech/qbs,villytiger/qbs,qt-labs/qbs,villytiger/qbs,gatzka/qt-labs-qbs,qtproject/qt-labs-qbs,villytiger/qbs,villytiger/qbs,qt-labs/qbs,Distrotech/qbs,qtproject/qt-labs-qbs,gatzka/qt-labs-qbs,Distrotech/qbs,gatzka/qt-labs-qbs,qt-labs/qbs,villytiger/qbs,Distrotech/qbs,gatzka/qt-labs-qbs,qtproject/qt-labs-qbs,Distrotech/qbs,Distrotech/qbs,qtproject/qt-labs-qbs,qt-labs/qbs