patch 8.2.2671: error for line number in legacy script

Problem:    Error for line number in legacy script.
Solution:   Check for number type.

src/typval.c

@@ -1621,11 +1621,12 @@ tv_get_lnum(typval_T *argvars)
 
     if (argvars[0].v_type != VAR_STRING || !in_vim9script())
 	lnum = (linenr_T)tv_get_number_chk(&argvars[0], NULL);
-    if (lnum < 0)  // no valid number, try using arg like line()
+    if (lnum <= 0 && argvars[0].v_type != VAR_NUMBER)
     {
 	int	fnum;
 	pos_T	*fp = var2fpos(&argvars[0], TRUE, &fnum, FALSE);
 
+	// no valid number, try using arg like line()
 	if (fp != NULL)
 	    lnum = fp->lnum;
     }

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2671,
 /**/
     2670,
 /**/