fix embed map bug on firefox

[boney-bun]

fix #207

[boney-bun]

tested locally using three browsers (firefox, chrome, safari):

[codecov]

Codecov Report

Merging #376 into master-qgis_server will decrease coverage by 0.24%.
The diff coverage is n/a.

@@                  Coverage Diff                   @@
##           master-qgis_server     #376      +/-   ##
======================================================
- Coverage               41.07%   40.82%   -0.25%     
======================================================
  Files                     329      329              
  Lines                   25751    25751              
  Branches                 3389     3389              
======================================================
- Hits                    10576    10513      -63     
- Misses                  14543    14608      +65     
+ Partials                  632      630       -2

Impacted Files	Coverage Δ
geonode/services/tests.py	75% <0%> (-17.5%)	⬇️
geonode/services/views.py	26.32% <0%> (-6.73%)	⬇️
geonode/utils.py	54.15% <0%> (-1.27%)	⬇️
geonode/layers/models.py	76.51% <0%> (-0.72%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ddc0aba...1d28659. Read the comment docs.

[boney-bun]

i'll bring this into testing