fix: Re-set SVG renderer aspect ratio after load (#6334)

The `QSvgRenderer::setAspectRatioMode` function only sets the aspect
ratio setting for the currently loaded SVG document.
https://github.com/qt/qtsvg/blob/29c3b512d9ca25941b18f7ee52ce8b80f003f3b4/src/svg/qsvgrenderer.cpp#L311-L320

When the theme changes, or we otherwise call load, this does not retain
our aspect ratio settings.
https://github.com/qt/qtsvg/blob/29c3b512d9ca25941b18f7ee52ce8b80f003f3b4/src/svg/qsvgrenderer.cpp#L412-L432

This means we need to ensure we re-set the SVG renderer's aspect ratio
after calling load.

src/widgets/buttons/SvgButton.cpp

@@ -19,7 +19,7 @@ SvgButton::SvgButton(Src source, BaseWidget *parent, QSize padding)
 void SvgButton::setSource(Src source)
 {
     this->source_ = std::move(source);
-    this->svg_->load(this->currentSvgPath());
+    this->loadSource();
     this->invalidateContent();
 }
 
@@ -48,7 +48,7 @@ void SvgButton::themeChangedEvent()
     {
         return;
     }
-    this->svg_->load(this->currentSvgPath());
+    this->loadSource();
     this->invalidateContent();
 }
 
@@ -98,4 +98,10 @@ QString SvgButton::currentSvgPath() const
     return this->source_.dark;
 }
 
+void SvgButton::loadSource()
+{
+    this->svg_->load(this->currentSvgPath());
+    this->svg_->setAspectRatioMode(Qt::KeepAspectRatio);
+}
+
 }  // namespace chatterino

src/widgets/buttons/SvgButton.hpp

@@ -72,6 +72,8 @@ protected:
 private:
     [[nodiscard]] QString currentSvgPath() const;
 
+    void loadSource();
+
     Src source_;
     QSvgRenderer *svg_;
     QSize padding_;