there's no default ScMatrixMode enum other than the known ones

... and if there was one not handled let the compiler complain.

Change-Id: Ibe3a2a913edfbfbba30a83a8d985d5509853ff6d

sc/source/core/tool/chgtrack.cxx

@@ -1689,8 +1689,6 @@ ScChangeActionContentCellType ScChangeActionContent::GetContentCellType( const S
                     return SC_CACCT_MATORG;
                 case MM_REFERENCE :
                     return SC_CACCT_MATREF;
-                default:
-                    ;
             }
             return SC_CACCT_NORMAL;
         }

sc/source/ui/docshell/docsh3.cxx

@@ -1003,8 +1003,6 @@ void ScDocShell::MergeDocument( ScDocument& rOtherDoc, bool bShared, bool bCheck
                                 break;
                                 case MM_REFERENCE :     // do nothing
                                 break;
-                                default:
-                                    OSL_FAIL( "MergeDocument: unknown MatrixFlag" );
                             }
                         }
                         break;