Fixing some migration rule bugs

tools/rosbag/scripts/makerule.py

@@ -75,7 +75,7 @@ if __name__ == '__main__':
     else:
         append_rule = []
 
-    f = open(sys.argv[1])
+    f = open(args[0])
     if f is None:
         print >> sys.stderr, 'Could not open message full definition: %s'
         sys.exit()

tools/rosbag/src/rosbag/migration.py

@@ -260,6 +260,8 @@ class MessageUpdateRule(object):
 
         # Instantiate types dynamically based on definition
         try:
+            if self.old_type == "":
+                raise Exception
             self.old_types = roslib.genpy.generate_dynamic(self.old_type, self.old_full_text)
             self.old_class = self.old_types[self.old_type]
             self.old_md5sum = self.old_class._md5sum
@@ -269,6 +271,8 @@ class MessageUpdateRule(object):
             self.old_md5sum = ""
 
         try:
+            if self.new_type == "":
+                raise Exception
             self.new_types = roslib.genpy.generate_dynamic(self.new_type, self.new_full_text)
             self.new_class = self.new_types[self.new_type]
             self.new_md5sum = self.new_class._md5sum