Don't auto-refresh the Array/Matrix visualizers when the program exits

gdb reports the exit as a *stopped event (reason="exited-*"), so with
the Auto checkbox checked the visualizers fired one last refresh on a
process that no longer exists, logging "unable to read memory" errors.

src/SeerMatrixVisualizerWidget.cpp

@@ -417,8 +417,9 @@ void SeerMatrixVisualizerWidget::handleText (const QString& text) {
             matrixStrideLineEdit->setFocus();
         }
 
-    // At a stopping point, refresh.
-    }else if (text.startsWith("*stopped,reason=\"")) {
+    // At a stopping point, refresh. Skip the "exited" reasons: the program
+    // is gone and reading the matrix would fail with a memory error.
+    }else if (text.startsWith("*stopped,reason=\"") && text.startsWith("*stopped,reason=\"exited") == false) {
 
         if (autoRefreshCheckBox->isChecked()) {
             handleRefreshButton();