substitute divider with separator + allow no transform function

Author: [email protected]

src/block/divider/index.js

@@ -15,6 +15,7 @@ import schema from './schema'
 import metadata from './block.json'
 import example from './example'
 import deprecated from './deprecated'
+import substitute from './substitute'
 
 export const settings = {
 	...metadata,
@@ -30,4 +31,5 @@ export const settings = {
 	deprecated,
 	edit,
 	save,
+	substitute,
 }

src/block/divider/substitute.js

@@ -0,0 +1,6 @@
+export const substitute = {
+	from: 'stackable/divider',
+	to: 'core/separator',
+}
+
+export default substitute

src/util/blocks.js

@@ -538,6 +538,9 @@ export const substituteCoreIfDisabled = ( blockName, blockAttributes, innerBlock
 			return substitutionRule.transform( blockAttributes, innerBlocks, disabledBlocks )
 		}
 		if ( blockName in disabledBlocks && disabledBlocks[ blockName ] === BLOCK_STATE.DISABLED ) { // eslint-disable-line camelcase
+			if ( ! substitutionRule.transform ) {
+				return [ substitutionRule.to, {} ]
+			}
 			return [ substitutionRule.to, substitutionRule.transform( blockAttributes, innerBlocks ) ]
 		}
 	}