Debugger: Fix crash in context menu builder.

A value node might not have a location due to e.g. issues resolving its parent.
Guard against this case and simply return early as we won't be able to take any
meaningful actions on such a node. Fixes the second crash listed in #10781.

src/apps/debugger/user_interface/gui/team_window/VariablesView.cpp

@@ -2042,6 +2042,9 @@ VariablesView::_GetContextActionsForNode(ModelNode* node,
 	ContextActionList* actions)
 {
 	ValueLocation* location = node->NodeChild()->Location();
+	if (location == NULL)
+		return B_OK;
+
 	status_t result = B_OK;
 	BMessage* message = NULL;