Crash when I have an empty code mark after one or more non-empty code marks.

[ghv]

• Provide a description of what the bug is about
• Provide a minimal code snippet / example that reproduces the bug.
• Provide a description of what you believe the output show be.

I am seeing a crash, "Fatal error: Index out of range" in updateBeginEndTailComments when the input looks like this:

            import Foundation
            import AppKit

            /*SVMPREFS
            S main | | RALL

            V Bool | boolVar1    | boolVar2 | IS |
            V Bool | hasBoolVar2 | boolVar2 | |
            V Bool | boolVar3    | boolVar3 | |
            V Bool | boolVar4    | boolVar4 | |

            S copy | | RALL

            V Bool | boolVar3 | boolVar3 | |
            V Bool | boolVar4 | boolVar4 | |

            M main | copy   | boolVar3 | boolVar3
            M main | copy   | boolVar4 | boolVar4
            M main | delete | hasBoolVar2

            SVMPREFS*/

            class MyMigrationTests {
                // MARK: BEGIN main
                // this will be deleted
                // MARK: END main

                // MARK: BEGIN copy
                // this will be deleted
                // MARK: END copy

                // MARK: BEGIN migrate
                // MARK: END migrate
            }

The migrate code mark has no code to delete and is therefore not having its code mark begin and code mark end indexes updated when removing the existing code between all code marks.

It should adjust these indexes because there are code marks for which there was some code to be deleted above it.

It is also possible that this would not crash if there are more lines after the empty code marks equal or greater in length to the number of lines removed in prior code marks. In this case the code would get inserted in the wrong place.