SDLPP: don't cause an exception when TextRenderer has an empty string

sdlpp/sdlpp_textrenderer.cpp

@@ -78,6 +78,10 @@ void TextRenderer::render() {
     }
 }
 void TextRenderer::updateTexture() {
+    if(_text.empty()) {
+        texture = NULL;
+        return;
+    }
     int fontSize = 0.6 * getRect().h;
     _config->getFont()->changeFontSize( fontSize );
     int intOutline = _config->getOutlineSize();