GPencil: Fix unreported problems painting after import SVG

After doing an import, the bounding box of the stroke was not calculated and any operation related to brushes (Sculpt, Weight Paint and Vertex Paint) was not working as expected because the bounding box of the stroke was wrong.

This problem was solved automatically after any edit operation, but must be solved in the import process.

source/blender/io/gpencil/intern/gpencil_io_import_svg.cc

@@ -148,6 +148,8 @@ bool GpencilImporterSVG::read()
         for (bGPDspoint &pt : MutableSpan(gps->points, gps->totpoints)) {
           sub_v3_v3(&pt.x, gp_center);
         }
+        /* Calc stroke bounding box. */
+        BKE_gpencil_stroke_boundingbox_calc(gps);
       }
     }
   }