diff --git a/relational.py b/relational.py
index 06a6996..33cb75f 100755
--- a/relational.py
+++ b/relational.py
@@ -82,8 +82,6 @@ if __name__ == "__main__":
     if x11:
         import signal
         signal.signal(signal.SIGINT, signal.SIG_DFL)
-
-        import sip  # needed on windows
         from PyQt5 import QtWidgets
         try:
             from relational_gui import guihandler, about, surveyForm
diff --git a/relational/optimizer.py b/relational/optimizer.py
index 9de4444..5637b96 100644
--- a/relational/optimizer.py
+++ b/relational/optimizer.py
@@ -39,7 +39,8 @@ def optimize_program(code: str, rels: Dict[str, Relation]) -> str:
     lines = code.split('\n')
     context: Dict[str, Node] = {}
 
-    for line in  lines:
+    last_res = None
+    for line in lines:
         # skip comments or empty lines
         line = line.strip()
         if line.startswith(';') or not line:
@@ -51,6 +52,9 @@ def optimize_program(code: str, rels: Dict[str, Relation]) -> str:
         parsed = tree(query)
         _replace_leaves(parsed, context)
         context[res] = parsed
+
+    if last_res is None:
+        return ''
     node = optimize_all(context[last_res], rels, tostr=False)
     return querysplit.split(node, rels)
 
diff --git a/relational/relation.py b/relational/relation.py
index 4524834..1984ec7 100644
--- a/relational/relation.py
+++ b/relational/relation.py
@@ -113,7 +113,7 @@ class Relation:
         format as defined in RFC4180.
         '''
         import csv
-        with open(filename, 'w') as fp:
+        with open(filename, 'w', newline='\n') as fp:
             writer = csv.writer(fp)  # Creating csv writer
 
             # It wants an iterable containing iterables
@@ -193,7 +193,7 @@ class Relation:
                 if eval(c_expr, attributes):
                     content.append(i)
             except Exception as e:
-                raise Exception(f'Failed to evaluate {expr} with {attributes}\n{e}')
+                raise Exception(f'Failed to evaluate {expr} with {i}\n{e}')
         return Relation(self.header, frozenset(content))
 
     def product(self, other: 'Relation') -> 'Relation':