VST3: Fixed a potential crash that could occur if a host sets the scale factor after closing the plug-in editor, and ensure that the last scale factor is re-used when opening the editor

modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp

@@ -844,6 +844,10 @@ private:
             macHostWindow = juce::attachComponentToWindowRefVST (component.get(), parent, isNSView);
            #endif
 
+           #if ! JUCE_MAC
+            setContentScaleFactor ((Steinberg::IPlugViewContentScaleSupport::ScaleFactor) scaleFactor);
+           #endif
+
             component->resizeHostWindow();
             systemWindow = parent;
             attachedToParent();
@@ -959,12 +963,17 @@ private:
         tresult PLUGIN_API setContentScaleFactor (Steinberg::IPlugViewContentScaleSupport::ScaleFactor factor) override
         {
            #if ! JUCE_MAC
+            scaleFactor = static_cast<float> (factor);
+
+            if (component == nullptr)
+                return kResultFalse;
+
             #if JUCE_WINDOWS && ! JUCE_WIN_PER_MONITOR_DPI_AWARE
              if (auto* ed = component->pluginEditor.get())
-                 ed->setScaleFactor ((float) factor);
+                 ed->setScaleFactor (scaleFactor);
             #else
-            if (! approximatelyEqual (component->getNativeEditorScaleFactor(), (float) factor))
-                component->nativeScaleFactorChanged ((double) factor);
+            if (! approximatelyEqual (component->getNativeEditorScaleFactor(), scaleFactor))
+                component->nativeScaleFactorChanged ((double) scaleFactor);
             #endif
 
             component->resizeHostWindow();
@@ -1198,6 +1207,8 @@ private:
        #if JUCE_MAC
         void* macHostWindow = nullptr;
         bool isNSView = false;
+       #else
+        float scaleFactor = 1.0f;
        #endif
 
        #if JUCE_WINDOWS