Added a check for empty risk model files [skip hazardlib][demos]
Added a check for empty risk model files [skip hazardlib][demos]


Former-commit-id: f55efd2ba646cd38820f979a8c883414f6fa102c [formerly c2e0e6b5fb78825fb67b9bbda6a3f06f312d0de5]
Former-commit-id: 718b23dddd2a33c29963b3d6f35514d6d8acf002
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine