Add placeholder value for INTERFACE64

Empty value causes comparison error.

Author: matthew-brett

.github/workflows/build.yml

@@ -18,7 +18,7 @@ jobs:
     strategy:
       matrix:
         BUILD_BITS: [64, 32]
-        INTERFACE64: ['1', '']
+        INTERFACE64: ['1', '0']
         os: [windows-latest]
         exclude:
           - BUILD_BITS: 32