Tested in SMW 1.7.0.2:
Produces "0" when there are no results:
{{#ask: [[Category:Existing category]] | format=count }}
{{#ask: [[Existing property name::any property value]] | format=count }}
{{#ask: [[Non-existing property name::any property value]] | format=count }}
Produces nothing when there are no results:
{{#ask: [[Category:Non-existing category]] | format=count }}
Version: unspecified
Severity: normal
The Semantic MediaWiki developers requested in https://phabricator.wikimedia.org/T64114 to move their task tracking to https://github.com/SemanticMediaWiki/SemanticMediaWiki/issues and to close remaining tasks in Wikimedia Phabricator. If you still face the problem reported in this task in a supported version of SMW, please feel free to transfer your report to https://github.com/SemanticMediaWiki/SemanticMediaWiki/issues . We are sorry for the inconvenience.