Fix infinite loop when deleting columns from wxTreeListCtrl.

Wrong variable was checked in the loop adjusting the columns values resulting
in an infinite loop.

Closes #16955.

docs/changes.txt

@@ -584,6 +584,7 @@ Unix:
 
 All (GUI):
 
+- Fix hang when deleting columns from wxTreeListCtrl.
 - Fix several floating point rounding bugs in wxPropertyGrid (Artur Wieczorek).
 - Restore support for wxFD_OVERWRITE_PROMPT and wxFD_FILE_MUST_EXIST in
   wxGenericFileDialog which was accidentally lost some time ago (Carl Godkin).

src/generic/treelist.cpp

@@ -170,10 +170,15 @@ public:
 
         wxScopedArray<wxString> oldTexts(m_columnsTexts);
         m_columnsTexts = new wxString[numColumns - 2];
+
+        // As above, n is the index in the new column texts array and m is the
+        // index in the old one.
         for ( unsigned n = 1, m = 1; n < numColumns - 1; n++, m++ )
         {
-            if ( n == col )
+            if ( m == col )
             {
+                // Skip copying the deleted column and keep the new index the
+                // same (so compensate for "n++" done in the loop).
                 n--;
             }
             else // Not the deleted column.