Handle the case where a virtual table xBestIndex method called while coding a trigger fired by a top-level statement with a RETURNING clause prepares a statement that also contains a RETURNING clause.

FossilOrigin-Name: ec6bffa3b0fbf7cdee852cb0208de1f5869dafd88e2ee64c23cec89634219adc

src/sqliteInt.h

@@ -4077,6 +4077,7 @@ struct Returning {
   int iRetCur;          /* Transient table holding RETURNING results */
   int nRetCol;          /* Number of in pReturnEL after expansion */
   int iRetReg;          /* Register array for holding a row of RETURNING */
+  char zName[40];       /* Name of trigger: "sqlite_returning_%p" */
 };
 
 /*