Remove a NEVER() that is no longer true. Fix for [36ffedcb9].

FossilOrigin-Name: 597896ed0ae9e2960a8f39576bd7f77a11dccc1da84b6a44ebb5c38d90ebc330
diff --git a/src/expr.c b/src/expr.c
index 9278673..a5f9a43 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -5449,12 +5449,13 @@
 ** Count the number of references to columns.
 */
 static int exprSrcCount(Walker *pWalker, Expr *pExpr){
-  /* The NEVER() on the second term is because sqlite3FunctionUsesThisSrc()
-  ** is always called before sqlite3ExprAnalyzeAggregates() and so the
-  ** TK_COLUMNs have not yet been converted into TK_AGG_COLUMN.  If
-  ** sqlite3FunctionUsesThisSrc() is used differently in the future, the
-  ** NEVER() will need to be removed. */
-  if( pExpr->op==TK_COLUMN || NEVER(pExpr->op==TK_AGG_COLUMN) ){
+  /* There was once a NEVER() on the second term on the grounds that
+  ** sqlite3FunctionUsesThisSrc() was always called before 
+  ** sqlite3ExprAnalyzeAggregates() and so the TK_COLUMNs have not yet 
+  ** been converted into TK_AGG_COLUMN. But this is no longer true due
+  ** to window functions - sqlite3WindowRewrite() may now indirectly call
+  ** FunctionUsesThisSrc() when creating a new sub-select. */
+  if( pExpr->op==TK_COLUMN || pExpr->op==TK_AGG_COLUMN ){
     int i;
     struct SrcCount *p = pWalker->u.pSrcCount;
     SrcList *pSrc = p->pSrc;