[BUGFIX] Correctly initialize content object for plugins

For rendering plugins FSC uses the cObjecViewHelper,
but misses to set the table name.

This leads to an incompletely initialized content object
being used when rendering the plugin.

cObj->currentRecord will stay empty, but some functionality
relies on this value to be correctly set.

Resolves: #76052
Releases: master, 7.6
Change-Id: I66b725adb3a0311609cfc60c29951eba5aa2217c
Reviewed-on: https://review.typo3.org/48011


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>