Empty file formats should not be visible at all

[christophfriedrich]

When there is no information on file formats because crawling /file_formats failed, the heading "File Formats (0)" is rendered anyway:

Interestingly, this behaviour is different for collections, processes and service types, which currently can't be crawled either on the backend in question, but are not rendered.

[christophfriedrich]

The Backend component does check whether fileFormats actually has content:

openeo-hub/src/components/Backend.vue

Line 60 in d83eef9

<FileFormats v-if="backend.fileFormats" :collapsed="true" :searchTerm="''" :formats="preparedBackend.fileFormats" :showInput="true" :showOutput="true"></FileFormats>

But the problem is that the backend never serves null, but instead this:

	"fileFormats": {
		"input": {},
		"output": null
	}

That is due to this MongoDB query:

openeo-hub/src/dbqueries.js

Lines 76 to 79 in d83eef9

	fileFormats: {
	input: { $ifNull: ['$fileFormats.input', {}] }, // input formats didn't exist in API v0.4 -> empty object as default
	output: { $ifNull: ['$fileFormats.output', '$fileFormats'] } // first item: API v1.0, second item: API v0.4
	},

It would be cleaner if the output would be fileFormats: null, but from the top of my head I couldn't come up with a quick Mongo query that does that.