[vala/0.48] glib-2.0: Fix criticals in string.joinv() with arrays that start with null

[Rico Tzschichholz <ricotz src gnome org>]

commit 78ba3e8823bcdbb3cb96b1b5028dce0a7174a107
Author: Nahuel Gomez <contact nahuelgomez com ar>
Date:   Tue Jan 25 14:23:58 2022 -0300

    glib-2.0: Fix criticals in string.joinv() with arrays that start with null

 tests/basic-types/strings.vala | 3 +++
 vapi/glib-2.0.vapi             | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/tests/basic-types/strings.vala b/tests/basic-types/strings.vala
index 99136bee1..c11342f11 100644
--- a/tests/basic-types/strings.vala
+++ b/tests/basic-types/strings.vala
@@ -53,6 +53,9 @@ void test_string_joinv () {
        s = string.joinv ("-", null);
        assert (s == "");
 
+       s = string.joinv ("-", { null });
+       assert (s == "");
+
        // LeakSanitizer -fsanitize=address
        sa.length = 3;
 }
diff --git a/vapi/glib-2.0.vapi b/vapi/glib-2.0.vapi
index 6b31dca9c..7d9b3c869 100644
--- a/vapi/glib-2.0.vapi
+++ b/vapi/glib-2.0.vapi
@@ -1213,7 +1213,7 @@ public class string {
                        len += ((!) separator).length * (i - 1);
 
                        string* res = GLib.malloc (len);
-                       void* ptr = string.copy_to_buffer ((void*) res, (!) str_array[0]);
+                       void* ptr = string.copy_to_buffer ((void*) res, (str_array[0] != null) ? ((!) 
str_array[0]) : "");
                        for (i = 1 ; i < str_array.length ; i++) {
                                ptr = string.copy_to_buffer (ptr, (!) separator);
                                ptr = string.copy_to_buffer (ptr, (str_array[i] != null) ? ((!) str_array[i]) 
: "");