fix: exception when saving dash

[amitmiran137]

SUMMARY

a bug sometimes happens when saving dash

bug.mov

this was the stacktrace from server

Traceback (most recent call last):
  File "/app/superset/views/base.py", line 162, in wraps
    return f(self, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/flask_appbuilder/security/decorators.py", line 151, in wraps
    return f(self, *args, **kwargs)
  File "/app/superset/utils/log.py", line 164, in wrapper
    value = f(*args, **kwargs)
  File "/app/superset/views/core.py", line 1183, in save_dash
    if remote_last_modified_time < current_last_modified_time:

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[codecov-io]

Codecov Report

Merging #13300 (5a4c017) into master (99a0c8a) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master   #13300   +/-   ##
=======================================
  Coverage   77.15%   77.15%           
=======================================
  Files         866      866           
  Lines       45005    45005           
  Branches     5357     5421   +64     
=======================================
+ Hits        34723    34725    +2     
+ Misses      10159    10157    -2     
  Partials      123      123           

Flag	Coverage Δ
cypress	58.51% <ø> (ø)
javascript	62.20% <ø> (ø)
python	80.81% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset/views/core.py	75.33% <100.00%> (ø)
superset/db_engine_specs/presto.py	88.46% <0.00%> (+0.42%)	⬆️

---

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 99a0c8a...5a4c017. Read the comment docs.

[junlincc]

@amitmiran137 thanks for the PR! 🙏
I have a couple of questions, appreciate if you can educate me.
what user actions trigger these errors usually?

before this change, how user find out the these errors? if you look at the end of the video you'll see the error in a popup with the entire stackstrace storming into the user's face

I tried changing the color schemes a few time in a row and this happend