fdo#35728: fix GridControl crash

* various forms.OGridControlModel tests segfaulted
* root cause is the migration to stl containers in DbGridControl
* the old tools container returned the removed pointer or NULL causing no failure
* a signed int was used as index while the functions returned a unsigned int
* the GRID_COLUMN_NOT_FOUND magic value was out of the signed range

svx/inc/svx/gridctrl.hxx

@@ -116,7 +116,7 @@ public:
     virtual void columnChanged() = 0;
 };
 
-#define GRID_COLUMN_NOT_FOUND   ((sal_uInt16)-1)
+#define GRID_COLUMN_NOT_FOUND   SAL_MAX_UINT16
 
 //==================================================================
 // InitWindowFacet, describing which aspect of a column's Window to (re-)initialize

svx/source/fmcomp/gridctrl.cxx

@@ -1722,13 +1722,13 @@ sal_uInt16 DbGridControl::AppendColumn(const XubString& rName, sal_uInt16 nWidth
 //------------------------------------------------------------------------------
 void DbGridControl::RemoveColumn(sal_uInt16 nId)
 {
-    sal_Int16 nIndex = GetModelColumnPos(nId);
-    DbGridControl_Base::RemoveColumn(nId);
-
-    delete m_aColumns[ nIndex ];
-    DbGridColumns::iterator it = m_aColumns.begin();
-    ::std::advance( it, nIndex );
-    m_aColumns.erase( it );
+    const sal_uInt16 nIndex = GetModelColumnPos(nId);
+    if(nIndex != GRID_COLUMN_NOT_FOUND)
+    {
+        DbGridControl_Base::RemoveColumn(nId);
+        delete m_aColumns[nIndex];
+        m_aColumns.erase( m_aColumns.begin()+nIndex );
+    }
 }
 
 //------------------------------------------------------------------------------