fix: add c_null_char to file name in diag manager output yaml test (#1604)

Author: J-Lentz

test_fms/parser/test_output_yaml.F90

@@ -203,11 +203,12 @@ program test_output_yaml
   call yaml_out_add_level2key( "order 4",k1(1))
   call yaml_out_add_level2key( "sides", k2(1))
   call yaml_out_add_level2key( "specials",  k2(2))
-  call write_yaml_from_struct_3 (trim(filename), 1, k1, v1, a2, k2, v2, a3, (/1, 1, 1, 1, 2, 1/), k3, v3, &
-                               & (/ 1, 1, 1 , 1, 0 ,0 ,0 ,0/))
+  call write_yaml_from_struct_3 (trim(filename) // c_null_char, 1, k1, v1, a2, k2, v2, a3, &
+                               & (/1, 1, 1, 1, 2, 1/), k3, v3, (/ 1, 1, 1 , 1, 0 ,0 ,0 ,0/))
 else
   !> Write the yaml
-  call write_yaml_from_struct_3 (trim(filename), 1, k1, v1, a2, k2, v2, a3, a3each, k3, v3,(/3, 0, 0, 0, 0, 0, 0, 0/))
+  call write_yaml_from_struct_3 (trim(filename) // c_null_char, 1, k1, v1, a2, k2, v2, a3, &
+                               & a3each, k3, v3, (/3, 0, 0, 0, 0, 0, 0, 0/))
 endif
 
 !> Check yaml output against reference