Catch colormap encoding issues

[vincentsarago]

When the colormap is wrongly encoded the application returns something like

{"detail":"Expecting value: line 1 column 1 (char 0)"}

We should try to catch this in

titiler/titiler/dependencies.py

Lines 80 to 85 in 3a6e5c5

	if colormap:
	return json.loads(
	colormap,
	object_hook=lambda x: {int(k): parse_color(v) for k, v in x.items()},
	)

and return a better error message