When using column span, the table must contains at least one row with non-null value

[andy176631]

When using column span, the table must contain at least one row with non-null value, otherwise exception happen. For example, I try...

final AsciiTable at = new AsciiTable();   
at.addRule();		
at.addRow("c_1_1", "c_1_2", "c_1_3");	
at.addRule();		
at.addRow("c_2_1", null, "c_2_3");		
at.addRule();
at.setTextAlignment(TextAlignment.CENTER);	
System.out.println(at.render());

The column spans are shown as expected:

┌──────────────────────────┬─────────────────────────┬─────────────────────────┐
│          c_1_1           │          c_1_2          │          c_1_3          │
├──────────────────────────┼─────────────────────────┴─────────────────────────┤
│          c_2_1           │                       c_2_3                       │
└──────────────────────────┴───────────────────────────────────────────────────┘

But if I removed the first row:

final AsciiTable at = new AsciiTable();   
at.addRule();		
at.addRow("c_2_1", null, "c_2_3");		
at.addRule();
at.setTextAlignment(TextAlignment.CENTER);	
System.out.println(at.render());

Exception occurred:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 80, Size: 80
	at java.util.ArrayList.rangeCheck(ArrayList.java:653)
	at java.util.ArrayList.get(ArrayList.java:429)
	at de.vandermeer.asciithemes.TA_GridHelpers.adjustBorder(TA_GridHelpers.java:194)
	at de.vandermeer.asciithemes.TA_Grid.addGrid(TA_Grid.java:306)
	at de.vandermeer.asciitable.AT_Renderer.renderAsCollection(AT_Renderer.java:282)
	at de.vandermeer.asciitable.AT_Renderer.render(AT_Renderer.java:128)
	at de.vandermeer.asciitable.AT_Renderer.render(AT_Renderer.java:112)
	at de.vandermeer.asciitable.AsciiTable.render(AsciiTable.java:185)
	at test.Test.main(Test.java:44)