Return an error message (instead of segfaulting) if test function fts5_expr() is invoked with no arguments.

FossilOrigin-Name: 8e818b8985c0196cd9671a6491796faaeebeb16e

ext/fts5/fts5_expr.c

@@ -1865,6 +1865,15 @@ static void fts5ExprFunction(
   Fts5Config *pConfig = 0;
   int iArg = 1;
 
+  if( nArg<1 ){
+    char *zErr = sqlite3_mprintf("wrong number of arguments to function %s",
+        bTcl ? "fts5_expr_tcl" : "fts5_expr"
+    );
+    sqlite3_result_error(pCtx, zErr, -1);
+    sqlite3_free(zErr);
+    return;
+  }
+
   if( bTcl && nArg>1 ){
     zNearsetCmd = (const char*)sqlite3_value_text(apVal[1]);
     iArg = 2;

ext/fts5/test/fts5eb.test

@@ -46,6 +46,13 @@ foreach {tn expr res} {
   do_execsql_test 1.$tn {SELECT fts5_expr($expr)} [list $res]
 }
 
+do_catchsql_test 2.1 {
+  SELECT fts5_expr()
+} {1 {wrong number of arguments to function fts5_expr}}
+
+do_catchsql_test 2.1 {
+  SELECT fts5_expr_tcl()
+} {1 {wrong number of arguments to function fts5_expr_tcl}}
 
 finish_test