[vala/0.40] vala: Report an internal error for unavailable context and bail

[Rico Tzschichholz <ricotz src gnome org>]

commit 4a62a1fe08d4900a8b625cfff3dfb8db266733f4
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sun Mar 1 12:37:52 2020 +0100

    vala: Report an internal error for unavailable context and bail
    
    If calling CodeContext.get/pop() with an empty stack present then there is
    no way to recover so bail.

 vala/valacodecontext.vala | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/vala/valacodecontext.vala b/vala/valacodecontext.vala
index d3955df70..8c3e15c65 100644
--- a/vala/valacodecontext.vala
+++ b/vala/valacodecontext.vala
@@ -258,6 +258,11 @@ public class Vala.CodeContext {
        public static CodeContext get () {
                List<CodeContext>* context_stack = context_stack_key.get ();
 
+               if (context_stack == null || context_stack->size == 0) {
+                       Report.error (null, "internal: No context available to get");
+                       assert_not_reached ();
+               }
+
                return context_stack->get (context_stack->size - 1);
        }
 
@@ -280,6 +285,11 @@ public class Vala.CodeContext {
        public static void pop () {
                List<CodeContext>* context_stack = context_stack_key.get ();
 
+               if (context_stack == null || context_stack->size == 0) {
+                       Report.error (null, "internal: No context available to pop");
+                       assert_not_reached ();
+               }
+
                context_stack->remove_at (context_stack->size - 1);
        }