patch 8.0.0266: compiler warning for using uninitialized variable

Problem:    Compiler warning for using uninitialized variable.
Solution:   Set tab_number also when there is an error.
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 0317050..1a10bb0 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -7533,7 +7533,10 @@
     else if (eap->addr_count > 0)
     {
 	if (unaccept_arg0 && eap->line2 == 0)
+	{
 	    eap->errmsg = e_invrange;
+	    tab_number = 0;
+	}
 	else
 	{
 	    tab_number = eap->line2;