make block writing a bit more readable.

pykat/finesse.py

@@ -393,7 +393,7 @@ class kat(object):
                     if values[1] == "FTblock":
                         newTag = values[2]
                         
-                        if self.__currentTag != None and newTag != self.__currentTag: 
+                        if self.__currentTag != None and self.__currentTag != NO_BLOCK: 
                             warnings.warn("found block {0} before block {1} ended".format(newTag, self.__currentTag))    
                             
                         if newTag in self.__blocks:
@@ -816,7 +816,8 @@ class kat(object):
         for key in self.__blocks:
             objs = self.__blocks[key].contents
 
-            if key != NO_BLOCK:
+            out.append("\n")
+            if key != NO_BLOCK and np.size(objs)>0:
                 out.append("%%% FTblock " + key + "\n")
             
             for obj in objs:
@@ -833,7 +834,7 @@ class kat(object):
                         else:
                             out.append(txt + "\n")
 
-            if key != NO_BLOCK:
+            if key != NO_BLOCK and np.size(objs)>0:
                 out.append("%%% FTend " + key + "\n")
             
         # now loop through all the nodes and get any gauss commands