WARNING: This could break something

If we have no data to update/draw, we avoid update/draw. On `DrawBuffersDefault()` if no vertes data is available nothing is drawn but some globals: vertexData, projection, modelview, draws... are reseted.

There shouldn't be any problem if we don't touch those globals in case no vertex have been processed but, just in case, I warn about it.

src/rlgl.h

@@ -1786,8 +1786,12 @@ void rlglClose(void)
 void rlglDraw(void)
 {
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
+    // Only process data if we have data to process
+    if (vertexData[currentBuffer].vCounter > 0)
+    {
         UpdateBuffersDefault();
         DrawBuffersDefault();       // NOTE: Stereo rendering is checked inside
+    }
 #endif
 }