fix control may reach end of non void function

agui2/src/Graphics/Dialogs/OutputDialog.cpp

@@ -110,7 +110,7 @@ TabType OutputDialog::getCurrentTabType() const {
         return TabType::Image;
     }
-    throw std::logic_error ( "Invalid tab type" );
+    throw std::logic_error ( "Invalid tab type." );
 }
 std::pair<QString, QString> OutputDialog::getCurrentTabFileFilter() const {

agui2/src/GraphvizIntegrator.cpp

@@ -9,7 +9,8 @@ QString selectFormat(GraphvizIntegrator::PictureFormat format) {
         case GraphvizIntegrator::PictureFormat::SVG:
             return "svg";
     }
-    Q_ASSERT(false);
+
+    throw std::logic_error ( "Invalid picture format." );
 }
 namespace GraphvizIntegrator {
@@ -56,4 +57,4 @@ namespace GraphvizIntegrator {
             return PNG;
         throw std::runtime_error { "Failed to determine output format from filename." };
     }
-}
+}
\ No newline at end of file