fixes copy of nu from source simulation

TurTLE/DNS.py

@@ -537,10 +537,10 @@ class DNS(_code):
             if os.path.exists(src_file_name):
                 # open source file for use later
                 src_file = h5py.File(src_file_name, 'r')
+            else:
                 print('TurTLE WARNING: unable to copy parameters of source simulation.'
                     + 'File {0} is missing.\n'.format(src_file_name)
                     + 'DNS will use default values for physical parameters.\n')
-            else:
                 src_file = None
         else:
             src_file = None
@@ -634,6 +634,7 @@ class DNS(_code):
                 opt.nu = type(self.parameters['nu'])(
                         src_file['parameters/nu'][()])
             # empirical viscosity based on forcing type
+            else:
                 if opt.forcing_type == 'fixed_energy_injection_rate':
                     # use the fact that mean dissipation rate is equal to injection rate
                         opt.nu = (