Added exception EObjectCheck for object reference check (runtime error 210).

rtl/objpas/sysconst.pp:
  + add resourcestring SObjectCheckError
rtl/objpas/sysutilh.inc:
  + add new Exception descendant EObjectCheck
rtl/objpas/sysutils.inc:
  + use EObjectCheck with message SObjectCheckError for runtime error 210


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@23656 3ad0048d-3df7-0310-abae-a5850022a9f2