Show better error message when Model class isn't abstract

[maherp1]

Describe the Bug
When you extend the ORM Model to your own Model and forget to set it to abstract, you get an Exception saying

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.lang.reflect.Field.getType()" because the return value of "org.javawebstack.orm.TableInfo.getField(String)" is null
	at org.javawebstack.orm.TableInfo.getIdType(TableInfo.java:282)
	at org.javawebstack.orm.TableInfo.analyzeTable(TableInfo.java:95)
	at org.javawebstack.orm.TableInfo.constructInfo(TableInfo.java:61)
	at org.javawebstack.orm.TableInfo.<init>(TableInfo.java:56)
	at org.javawebstack.orm.Repo.<init>(Repo.java:35)
	at org.javawebstack.orm.ORM.register(ORM.java:25)
	at org.javawebstack.orm.ORM.register(ORM.java:37)

To Reproduce
Steps to reproduce the behavior:

1. Forget to set your model class to abstract

Expected behavior
Maybe show some better error message which indicates that your base model isn't abstract yet.

Environment Information:

• Java Language Level 21
• ORM Version 1.0.3-SNAPSHOT