When I install the module MaintenanceMode then I get this error message:
Breaking news… Fatal Error: Uncaught Error: Access to undeclared static property: MaintenanceMode::$fM in site/modules/MaintenanceMode/MaintenanceMode.module:94
#0 [internal function]: MaintenanceMode::getModuleConfigInputfields(Array)
#1 wire/core/Modules.php (3903): call_user_func(Array, Array)
#2 wire/core/Wire.php (400): Modules->___getModuleConfigInputfields('MaintenanceMode', Object(InputfieldForm))
#3 wire/core/WireHooks.php (823): Wire->_callMethod('___getModuleCon...', Array)
#4 wire/core/Wire.php (465): WireHooks->runHooks(Object(Modules), 'getModuleConfig...', Array)
#5 wire/modules/Process/ProcessModule/ProcessModule.module (1349): P (line 94 of site/modules/MaintenanceMode/MaintenanceMode.module)
What can I do?