Merge topic 'cmake-gui-incidental-errors' into release-3.31

e9c494005c cmake-gui: Fix regression that prints an incidental error on fresh build trees

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !10429

Source/QtDialog/QCMake.cxx

@@ -94,7 +94,8 @@ void QCMake::setSourceDirectory(const QString& _dir)
     emit this->sourceDirChanged(this->SourceDirectory);
     this->loadPresets();
     this->setPreset(QString{});
-    if (!cmSystemTools::FileIsFullPath(
+    if (!this->MaybeRelativeBinaryDirectory.isEmpty() &&
+        !cmSystemTools::FileIsFullPath(
           this->MaybeRelativeBinaryDirectory.toStdString())) {
       this->setBinaryDirectory(this->MaybeRelativeBinaryDirectory);
     }