Add error msg for null file while Adding Commercial for event

[AnkushMalik]

Null file error message added for uploading empty file in CommercialsController#mass_upload

Closes #1959

Checklist

• I have read the Contribution & Best practices Guide.
• My branch is up-to-date with the upstream master branch.
• The tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works(if appropriate).
• I have added necessary documentation (if appropriate).

Short description of what this resolves/which issues does this fix?:

• Null file error msg required on adding commercials, Null file validation required on adding commercials #1959

[bear454]

Are there any other conditions that could cause an error here?

[AnkushMalik]

yes when user clicks on add commercial without selecting any file 'errors' in line 58^ is nil, it redirects him to error page:

So, i thought there should be a error msg with redirecting user back

[AnkushMalik]

@bear454, is there any problem with this issue or PR? can you please review this :-) ?

[bear454]

I think you misunderstood my question - I read your code as treating any error as a result of a bad file upload; have you considered that other conditions may cause errors ?

[AnkushMalik]

oh, my bad, now I understand my mistake thanks :-)

[bear454]

👍