Changed the check whether to invoke a property in the v-tables to work around the non-shared methods in v-tables. Set the function signature to an empty string rather that null by default.

Signed-off-by: Dimitar Dobrev <dpldobrev@yahoo.com>
Merge pull request #105 from ddobrev/master

Changed the check whether to invoke a property in the v-tables to work around the non-shared methods in v-tables