Allow a new API key to be generated if the existing apikey.txt file has been deleted

.gitignore

@@ -30,4 +30,4 @@
 /tmp
 /data*
 /src/test/resources/arbitrary/*/.qortal/cache
-apikey
+apikey.txt

src/main/java/org/qortal/api/ApiKey.java

@@ -86,6 +86,10 @@ public class ApiKey {
         return (this.apiKey != null);
     }
 
+    public boolean exists() {
+        return this.getFilePath().toFile().exists();
+    }
+
     @Override
     public String toString() {
         return this.apiKey;

src/main/java/org/qortal/api/resource/AdminResource.java

@@ -735,7 +735,7 @@ public class AdminResource {
 		ApiKey apiKey = Security.getApiKey(request);
 
 		// If the API key is already generated, we need to authenticate this request
-		if (apiKey.generated()) {
+		if (apiKey.generated() && apiKey.exists()) {
 			Security.checkApiCallAllowed(request);
 		}