Fix problems with precision of new bounding spheres

glm::length => squared computation => we need the double precision in the computation. Got bounding sphere values of "inf" for a few large renderables (the DU grids)...

modules/base/rendering/grids/renderablegrid.cpp

@@ -243,7 +243,7 @@ void RenderableGrid::update(const UpdateData&) {
         _varray[nr++] = { halfSize.x, y1, 0.f };
     }
 
-    setBoundingSphere(static_cast<double>(glm::length(halfSize)));
+    setBoundingSphere(glm::length(glm::dvec2(halfSize)));
 
     glBindVertexArray(_vaoID);
     glBindBuffer(GL_ARRAY_BUFFER, _vBufferID);