running cavern on svx files improved

parsers/survex.py

@@ -1221,8 +1221,14 @@ class LoadingSurvex():
             self.caverncount += 1
             
             # should also collect all the .err files too and create a DataIssue for each one which 
-            # - is nonzero in size
+            # - is nonzero in size AND
             # - has Error greater than 5% anywhere, or some other more serious error
+            
+            errpath = Path(fullpath + ".err")
+            if errpath.is_file():
+                if errpath.stat().st_size == 0:
+                    errpath.unlink() # delete empty closure error file
+
 
         svxpath = Path(fullpath + ".svx")
         logpath = Path(fullpath + ".log")