Fix bug in workflow job enkf_job_scale_std_correlated:

[joakim-hove]

This trace-back/bug comes from a situtation where some realisations have failed and there is missing data. We must be more robust to that in the function: enkf_main_std_scale_correlated_obs_JOB()

Abort called from: __hash_get_node (/var/jenkins/jenkins-be/workspace/komodo/cache/libecl-master/lib/util/hash.cpp:90)

Error message: __hash_get_node: tried to get from key:WOPT:A-16HP.115 which does not exist - aborting



--------------------------------------------------------------------------------
 #00 util_abort__(..)                                                              in ??:0
 #01 ???(..)                                                                       in hash.cpp:0
 #02 hash_get(..)                                                                  in ??:0
 #03 block_fs_fread_realloc_buffer(..)                                             in ??:0
 #04 ???(..)                                                                       in block_fs_driver.cpp:0
 #05 ???(..)                                                                       in enkf_node.cpp:0
 #06 enkf_obs_get_obs_and_measure_node(..)                                         in ??:0
 #07 enkf_obs_get_obs_and_measure_data(..)                                         in ??:0
 #08 enkf_obs_scale_correlated_std(..)                                             in ??:0
 #09 enkf_main_std_scale_correlated_obs_JOB(..)                                    in ??:0
 #10 ffi_call_unix64(..)                                                           in /var/jenkins/jenkins-be/workspace/komodo/cache/Python-2.7.14/Modules/_ctypes/libffi/src/x86/unix64.S:79
 #11 ffi_call(..)                                                                  in /var/jenkins/jenkins-be/workspace/komodo/cache/Python-2.7.14/Modules/_ctypes/libffi/src/x86/ffi64.c:527