[vala/0.40] codegen: Don't pass CCodeFunctionCall to NULL-aware free macro

[Rico Tzschichholz <ricotz src gnome org>]

commit 09c8ce85584acfc70c247b30f6af42c186bea75e
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sun Sep 27 19:21:37 2020 +0200

    codegen: Don't pass CCodeFunctionCall to NULL-aware free macro
    
    This resulted in invalid C code:
        error: lvalue required as left operand of assignment

 codegen/valaccodebasemodule.vala | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/codegen/valaccodebasemodule.vala b/codegen/valaccodebasemodule.vala
index 9318bc721..b87cf2974 100644
--- a/codegen/valaccodebasemodule.vala
+++ b/codegen/valaccodebasemodule.vala
@@ -3568,6 +3568,8 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
                        // FIXME this breaks in our macro, so this should not happen
                        if (cvar is CCodeCastExpression) {
                                cvar = ((CCodeCastExpression) cvar).inner;
+                       } else if (cvar is CCodeFunctionCall) {
+                               cvar = ((CCodeFunctionCall) cvar).get_arguments ()[0];
                        }
 
                        ccall = new CCodeFunctionCall (new CCodeIdentifier (free0_func));