Update MetadataStorage.ts

Bugfix for "ERROR TypeError: Cannot read property 'prototype' of undefined" in decorator @Transform.

Author: tbreug

src/metadata/MetadataStorage.ts

@@ -146,19 +146,19 @@ export class MetadataStorage {
 
     private getMetadata<T extends { target: Function, propertyName: string }>(metadatas: T[], target: Function): T[] {
         const metadataFromTarget = metadatas.filter(meta => meta.target === target && meta.propertyName !== undefined);
-        const metadataFromChildren = metadatas.filter(meta => target.prototype instanceof meta.target && meta.propertyName !== undefined);
+        const metadataFromChildren = metadatas.filter(meta => target && target.prototype instanceof meta.target && meta.propertyName !== undefined);
         return metadataFromChildren.concat(metadataFromTarget);
     }
 
     private findMetadata<T extends { target: Function, propertyName: string }>(metadatas: T[], target: Function, propertyName: string): T {
         const metadataFromTarget = metadatas.find(meta => meta.target === target && meta.propertyName === propertyName);
-        const metadataFromChildren = metadatas.find(meta => target.prototype instanceof meta.target && meta.propertyName === propertyName);
+        const metadataFromChildren = metadatas.find(meta => target && target.prototype instanceof meta.target && meta.propertyName === propertyName);
         return metadataFromTarget || metadataFromChildren;
     }
 
     private findMetadatas<T extends { target: Function, propertyName: string }>(metadatas: T[], target: Function, propertyName: string): T[] {
         const metadataFromTarget = metadatas.filter(meta => meta.target === target && meta.propertyName === propertyName);
-        const metadataFromChildren = metadatas.filter(meta => target.prototype instanceof meta.target && meta.propertyName === propertyName);
+        const metadataFromChildren = metadatas.filter(meta => target && target.prototype instanceof meta.target && meta.propertyName === propertyName);
         return metadataFromChildren.reverse().concat(metadataFromTarget.reverse());
     }