Fix a regression in composition handling

FIX: Fix a regression in composition handling in 1.33.3 that occurs for some IMEs
when starting composition on an empty line.

Closes ProseMirror/prosemirror#1458

src/input.ts

@@ -526,7 +526,7 @@ export function findCompositionNode(view: EditorView) {
         return textAfter
     }
   }
-  return textBefore
+  return textBefore || textAfter
 }
 
 function timestampFromCustomEvent() {