Fix #7969, 'layer source' in vector properties is empty

- Revert part of 6c51965, where setting the line edit field was (accidentally?) removed
QGIS Server - GetPrint request does not respect text boxes size and position if dynamic content passed

This commit brings some correction for the issue #7894
Firstly the use of adjustSizeToText has been inactivate
Secondly if a composerLabel is not in the parameterMap the default value
is conserved.