Skip nullish values when merging the OldDot transition payload

Author: mikolajpochec

src/libs/actions/Session/index.ts

@@ -793,10 +793,17 @@ function setupNewDotAfterTransitionFromOldDot(hybridAppSettings: HybridAppSettin
             ];
 
             for (const [key, value] of Object.entries(newDotOnyxValues)) {
+                // `?? {}` used to stand in for a missing value, but these keys are not all objects —
+                // merging `{}` into SHOULD_USE_STAGING_SERVER leaves a truthy non-boolean behind. There is
+                // nothing to apply when OldDot sends nothing, so skip the key instead.
+                if (value === undefined || value === null) {
+                    continue;
+                }
+
                 onyxUpdates.push({
                     onyxMethod: Onyx.METHOD.MERGE,
                     key,
-                    value: value ?? {},
+                    value,
                 } as OnyxUpdate<keyof typeof newDotOnyxValues>);
             }