BuildManager: Fix crash in progressTextChanged()
BuildManager: Fix crash in progressTextChanged()

If we receive that signal after we've already finished, we might no
longer have a m_progressFutureInterface.

Task-number: QTCREATORBUG-11873
Change-Id: I19c48376a0fd0bf05aa6827fb8aae2f7a5f3151e
Reviewed-by: Daniel Teske <d8a411aec9a206efedb4d45b75fe8d13f1e2b628@digia.com>

AltarBeastiful/qt-creator,kuba1/qtcreator,danimo/qt-creator,xianian/qt-creator,kuba1/qtcreator,maui-packages/qt-creator,AltarBeastiful/qt-creator,martyone/sailfish-qtcreator,danimo/qt-creator,amyvmiwei/qt-creator,kuba1/qtcreator,omniacreator/qtcreator,colede/qtcreator,kuba1/qtcreator,Distrotech/qtcreator,AltarBeastiful/qt-creator,xianian/qt-creator,xianian/qt-creator,kuba1/qtcreator,omniacreator/qtcreator,Distrotech/qtcreator,colede/qtcreator,maui-packages/qt-creator,farseerri/git_code,martyone/sailfish-qtcreator,xianian/qt-creator,maui-packages/qt-creator,Distrotech/qtcreator,colede/qtcreator,xianian/qt-creator,colede/qtcreator,martyone/sailfish-qtcreator,amyvmiwei/qt-creator,maui-packages/qt-creator,danimo/qt-creator,amyvmiwei/qt-creator,omniacreator/qtcreator,danimo/qt-creator,AltarBeastiful/qt-creator,amyvmiwei/qt-creator,Distrotech/qtcreator,martyone/sailfish-qtcreator,farseerri/git_code,AltarBeastiful/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,amyvmiwei/qt-creator,colede/qtcreator,amyvmiwei/qt-creator,danimo/qt-creator,Distrotech/qtcreator,colede/qtcreator,danimo/qt-creator,Distrotech/qtcreator,martyone/sailfish-qtcreator,AltarBeastiful/qt-creator,farseerri/git_code,farseerri/git_code,danimo/qt-creator,martyone/sailfish-qtcreator,omniacreator/qtcreator,maui-packages/qt-creator,colede/qtcreator,farseerri/git_code,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,Distrotech/qtcreator,kuba1/qtcreator,maui-packages/qt-creator,kuba1/qtcreator,kuba1/qtcreator,omniacreator/qtcreator,xianian/qt-creator,kuba1/qtcreator,farseerri/git_code,omniacreator/qtcreator,danimo/qt-creator,farseerri/git_code,AltarBeastiful/qt-creator,xianian/qt-creator,xianian/qt-creator,danimo/qt-creator,martyone/sailfish-qtcreator,omniacreator/qtcreator,martyone/sailfish-qtcreator,amyvmiwei/qt-creator,maui-packages/qt-creator,farseerri/git_code