fixed segfaults on startup

...killManagerPlugin/SkillManagerMonitorWidgetController.cpp

.../SkillManagerPlugin/SkillManagerMonitorWidgetController.h

source/RobotAPI/libraries/skills_gui/SkillMemoryGui.cpp

source/RobotAPI/libraries/skills_gui/SkillMemoryGui.h

...raries/skills_gui/executions/SkillExecutionTreeWidget.cpp

...ibraries/skills_gui/executions/SkillExecutionTreeWidget.h

source/RobotAPI/libraries/skills_gui/gui_utils.cpp

source/RobotAPI/libraries/skills_gui/gui_utils.h

.../libraries/skills_gui/skill_details/ProfileMenuWidget.cpp

...PI/libraries/skills_gui/skill_details/ProfileMenuWidget.h

...braries/skills_gui/skill_details/SkillDetailsGroupBox.cpp

...libraries/skills_gui/skill_details/SkillDetailsGroupBox.h

...aries/skills_gui/skill_details/SkillDetailsTreeWidget.cpp

...braries/skills_gui/skill_details/SkillDetailsTreeWidget.h

...ce/RobotAPI/libraries/skills_gui/skills/SkillGroupBox.cpp

source/RobotAPI/libraries/skills_gui/skills/SkillGroupBox.h