[vala/0.40] codegen: Check param for null before using it

[Rico Tzschichholz <ricotz src gnome org>]

commit 64ab2bf83c29982a0bc716aa1297373140744c12
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Wed Jul 22 10:16:39 2020 +0200

    codegen: Check param for null before using it
    
    Regression of 5490b0b21a4089d803d51c91311430d60d266f7b
    
    This caused criticals like:
    
      vala_get_ccode_array_length: assertion 'node != NULL' failed
    
    See https://gitlab.gnome.org/GNOME/vala/issues/929

 codegen/valaccodemethodcallmodule.vala |  2 +-
 tests/Makefile.am                      |  1 +
 tests/methods/varargs-ref.vala         | 14 ++++++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)
---
diff --git a/codegen/valaccodemethodcallmodule.vala b/codegen/valaccodemethodcallmodule.vala
index 317091d9c..33357527b 100644
--- a/codegen/valaccodemethodcallmodule.vala
+++ b/codegen/valaccodemethodcallmodule.vala
@@ -878,7 +878,7 @@ public class Vala.CCodeMethodCallModule : CCodeAssignmentModule {
 
                        // update possible stale _*_size_ variable
                        if (unary != null && unary.operator == UnaryOperator.REF) {
-                               if (get_ccode_array_length (param) && param.variable_type is ArrayType
+                               if (param != null && get_ccode_array_length (param) && param.variable_type is 
ArrayType
                                    && !((ArrayType) param.variable_type).fixed_length && ((ArrayType) 
param.variable_type).rank == 1) {
                                        unowned Symbol? array_var = unary.inner.symbol_reference;
                                        unowned LocalVariable? array_local = array_var as LocalVariable;
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 85d6a858d..18a8ccfde 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -178,6 +178,7 @@ TESTS = \
        methods/varargs-delegate-without-target.vala \
        methods/varargs-gvalue.vala \
        methods/varargs-out.vala \
+       methods/varargs-ref.vala \
        methods/varargs-struct.vala \
        control-flow/assigned-local-variable.vala \
        control-flow/break.vala \
diff --git a/tests/methods/varargs-ref.vala b/tests/methods/varargs-ref.vala
new file mode 100644
index 000000000..9c3f5fa74
--- /dev/null
+++ b/tests/methods/varargs-ref.vala
@@ -0,0 +1,14 @@
+void set_foo_varg (string s, ...) {
+       var args = va_list ();
+       string** ref_s1 = args.arg ();
+       *ref_s1 = "bar";
+       string** ref_s2 = args.arg ();
+       *ref_s2 = "manam";
+}
+
+void main () {
+       unowned string bar = "", manam = "";
+       set_foo_varg ("foo", ref bar, ref manam);
+       assert (bar == "bar");
+       assert (manam == "manam");
+}