Add no-metadata message.
Add no-metadata message.

If an image has no metadata, show a message in the UI acknowledging this
rather than a blank panel.

azavea/raster-foundry,raster-foundry/raster-foundry,aaronxsu/raster-foundry,azavea/raster-foundry,aaronxsu/raster-foundry,aaronxsu/raster-foundry,azavea/raster-foundry,kdeloach/raster-foundry,kdeloach/raster-foundry,kdeloach/raster-foundry,kdeloach/raster-foundry,raster-foundry/raster-foundry,kdeloach/raster-foundry,aaronxsu/raster-foundry,azavea/raster-foundry,azavea/raster-foundry,raster-foundry/raster-foundry