Improve error message when nSoil_Types higher than actual classes
When nSoil_Types in the header of soil_classdefinition.txt is lower than the actual classes defined, an error will be raised that class n is missing.
If it is higher than the actual classes defined, mHM will return a Segmentation fault (SIGSEGV):
Program received signal SIGSEGV: Segmentation fault - invalid memory reference. Backtrace for this error: #0 0x2B7084854347 #1 0x2B708485494E #2 0x2B70863863FF #3 0x54FFB4 in __mo_soil_database_MOD_generate_soil_database #4 0x55A82C in __mo_mpr_startup_MOD_mpr_initialize #5 0x5C87D4 in __mo_startup_MOD_mhm_initialize #6 0x59119F in MAIN__ at mhm_driver.f90:? Segmentation fault
This makes it hard to identify the root cause of the error for the user