svg_loader: handling zero width/height viewbox

For svgs with the width and/or height value set to zero
rendering was disabled - the load api return Result:Unknown
and draw - Result::InsufficientCondition.
Now an empty scene is added, so that both, load and draw,
return Result::Success.

src/loaders/svg/tvgSvgLoader.cpp

@@ -3186,6 +3186,12 @@ SvgLoader::~SvgLoader()
 
 void SvgLoader::run(unsigned tid)
 {
+    //According to the SVG standard the value of the width/height of the viewbox set to 0 disables rendering
+    if (renderingDisabled) {
+        root = Scene::gen();
+        return;
+    }
+
     if (!simpleXmlParse(content, size, true, _svgLoaderParser, &(loaderData))) return;
 
     if (loaderData.doc) {
@@ -3316,7 +3322,7 @@ bool SvgLoader::read()
     if (((uint32_t)viewFlag & (uint32_t)SvgViewFlag::Viewbox) &&
         (fabsf(vw) <= FLT_EPSILON || fabsf(vh) <= FLT_EPSILON)) {
         TVGLOG("SVG", "The <viewBox> width and/or height set to 0 - rendering disabled.");
-        return false;
+        renderingDisabled = true;
     }
 
     TaskScheduler::request(this);

src/loaders/svg/tvgSvgLoader.h

@@ -54,6 +54,7 @@ private:
     SvgViewFlag viewFlag = SvgViewFlag::None;
     AspectRatioAlign align = AspectRatioAlign::XMidYMid;
     AspectRatioMeetOrSlice meetOrSlice = AspectRatioMeetOrSlice::Meet;
+    bool renderingDisabled = false;
 
     bool header();
     void clear();