[widgets][assetwidget] Add tooltip when asset is invalid
It follows the same idea as the experiment editor hinting. Fixes #264
| Status | Name | Job ID | Coverage | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Build | |||||||||
| passed | build_linux_36 |
#201055
docker
|
00:10:23
|
90.0% |
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| passed | build_linux_37 |
#201056
docker
|
00:10:13
|
90.0% |
|
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| passed | build_macosx_36 |
#201053
macosx
|
00:09:29
|
90.0% |
|
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| passed | build_macosx_37 |
#201054
macosx
|
00:09:05
|
90.0% |
|
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