ecere/gfx/drivers/GL: Automatically flushing matrices before switching shaders

- Matrix stacks get mixed up otherwise resulting in confusion

Author: jerstlouis

ecere/src/gfx/drivers/gl3/shaders.ec

@@ -313,7 +313,10 @@ public:
       if(!glCaps_shaders) return false;
 
       if(activeShader != this)
+      {
+         GLFlushMatrices(); // Must flush matrices before switching shader otherwise the matrix stacks may get mixed up
          activeShader = this;
+      }
 
       result = true;
       if(activeState != state || !shader)