From fd321588613472dfb31659f56961ffb0cbf9eb27 Mon Sep 17 00:00:00 2001
From: cyberrumor <46626673+cyberrumor@users.noreply.github.com>
Date: Wed, 19 Mar 2025 10:23:53 -0700
Subject: [PATCH] Fix crash when switching opened projects (#7797)

* Fix crash when switching opened projects #7793

When the DAW is already running with an open project and you attempt to
open another project via File > Open, a segfault used to occur.

The crash seems to have been caused by model()->value(), which was
called in Fader::getModelValueAsDbString(). The model() function
looked like it should return a pointer to an AutomatableModel.

I suspect that when a model was dropped in favor of loading models for
a new project, the AutomatableModel pointer became a null pointer.

Add a check to the AutomatableModel pointer so getModelValueAsDbString
returns early (before accessing member functions) if the pointer is
null. This fixes the crash.
---
 src/gui/widgets/Fader.cpp | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/gui/widgets/Fader.cpp b/src/gui/widgets/Fader.cpp
index 153d8ca1a..61e6e753d 100644
--- a/src/gui/widgets/Fader.cpp
+++ b/src/gui/widgets/Fader.cpp
@@ -512,9 +512,16 @@ void Fader::modelValueChanged()
 
 QString Fader::getModelValueAsDbString() const
 {
-	const auto value = model()->value();
-
 	QString label(tr("Volume: %1 dB"));
+	// Check that the pointer isn't dangling, which can happen if the
+	// model was dropped in order to load a new project from an existing one.
+	auto* newModel = model();
+	if (!newModel)
+	{
+		// model() was a dangling pointer, so return a sane default value.
+		return label.arg(tr("-inf"));
+	}
+	const auto value = newModel->value();
 
 	if (modelIsLinear())
 	{