Quick patch to the Lemon parser template to avoid an array overread reported

by OSSFuzz.  A proper fix involves enhancements to the table generators in
Lemon to make the overread impossible.  That fix will take longer to
implement.  The current check-in is a stop-gap.

FossilOrigin-Name: 3f6730be4cb712a28401be6d96e56ccb3f2e98dd8961b477befec3f363715178

tool/lempar.c

@@ -550,6 +550,7 @@ static YYACTIONTYPE yy_find_shift_action(
 #if YY_SHIFT_MAX+YYWILDCARD>=YY_ACTTAB_COUNT
           j<YY_ACTTAB_COUNT &&
 #endif
+          j<sizeof(yy_lookahead)/sizeof(yy_lookahead[0]) &&
           yy_lookahead[j]==YYWILDCARD && iLookAhead>0
         ){
 #ifndef NDEBUG