Added a check on source_group.srcs_weights before saving them
Added a check on source_group.srcs_weights before saving them


Former-commit-id: 67726c27e9cf622e5e4ed6060b82d93f52765852 [formerly 67726c27e9cf622e5e4ed6060b82d93f52765852 [formerly 1dea014135c31d2e8d2158fe8ee0918cb5098487]]
Former-commit-id: 7d274a8c49d3b86a8dc2a1059ef41376005d526d
Former-commit-id: e6ab9b266971427c2b3e44f5144ca3220222c50c
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine