Avoid a crash when Zenmap can't read a script file

zenmap/zenmapCore/ScriptMetadata.py

@@ -363,6 +363,7 @@ class ScriptMetadata (object):
 
     def get_metadata(self, filename):
         entry = self.Entry(filename)
+        try:
             entry.description = self.get_string_variable(filename, "description")
             entry.arguments = self.get_arguments(entry.filename)
             entry.license = self.get_string_variable(filename, "license")
@@ -379,6 +380,8 @@ class ScriptMetadata (object):
                         entry.usage = tag_text
             finally:
                 f.close()
+        except IOError as e:
+            entry.description = "Error getting metadata: {}".format(e)
 
         return entry