Fix Build latest images on push event workflow (opea-project#1282)

Signed-off-by: ZePan110 <ze.pan@intel.com>
Signed-off-by: Dariusz Trawinski <Dariusz.Trawinski@intel.com>

Author: ZePan110

.github/workflows/push-image-build.yml

@@ -62,7 +62,7 @@ jobs:
 
   image-build:
     needs: get-build-matrix
-    if: ${{ fromJSON(needs.get-build-matrix.outputs.services).length != 0 }}
+    if: needs.get-build-matrix.outputs.services != '[]'
     strategy:
       matrix:
         service: ${{ fromJSON(needs.get-build-matrix.outputs.services) }}