Xcode 6 swift multiple segues with prepare for segue

Im currently working on an app with one main view controller and 2 other view controllers. One is my browser which is working fine and the other one is a table view. I have 5 buttons which lead me to my browser and one which should go to my table view. I've connected the button with a "present modally" segue to my table view controller(which has embed in a NavigationViewController. But every time I try to push the button the simulator crashes and this error appears:

libswiftCore.dylib`swift_dynamicCastClassUnconditional:
0x10b9bf860:  pushq  %rbp
0x10b9bf861:  movq   %rsp, %rbp
0x10b9bf864:  testq  %rdi, %rdi
0x10b9bf867:  je     0x10b9bf89e               ; swift_dynamicCastClassUnconditional + 62
0x10b9bf869:  movabsq $-0x7fffffffffffffff, %rax
0x10b9bf873:  testq  %rax, %rdi
0x10b9bf876:  jne    0x10b9bf89e               ; swift_dynamicCastClassUnconditional + 62
0x10b9bf878:  leaq   0xb52e9(%rip), %rax
0x10b9bf87f:  movq   (%rax), %rax
0x10b9bf882:  andq   (%rdi), %rax
0x10b9bf885:  nopw   %cs:(%rax,%rax)
0x10b9bf890:  cmpq   %rsi, %rax
0x10b9bf893:  je     0x10b9bf8ad               ; swift_dynamicCastClassUnconditional + 77
0x10b9bf895:  movq   0x8(%rax), %rax
0x10b9bf899:  testq  %rax, %rax
0x10b9bf89c:  jne    0x10b9bf890               ; swift_dynamicCastClassUnconditional + 48
0x10b9bf89e:  leaq   0x36b7d(%rip), %rax       ; "Swift dynamic cast failed"
0x10b9bf8a5:  movq   %rax, 0xb4c0c(%rip)       ; gCRAnnotations + 8
0x10b9bf8ac:  int3   
0x10b9bf8ad:  movq   %rdi, %rax
0x10b9bf8b0:  popq   %rbp
0x10b9bf8b1:  retq   
0x10b9bf8b2:  nopw   %cs:(%rax,%rax)

It won't work as well if I connect my segue to another viewcontroller or if I'm using other buttons.

I know the problem is somewhere in this code because if I delete it everything works just fine:

` override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {

    var DestViewConroller : WebViewController = segue.destinationViewController as WebViewController



    if (segue.identifier == "homeSegue"){

        DestViewConroller.url = "https://edu.sh.ch"


    }

    if (segue.identifier == "mailSegue"){

        DestViewConroller.url = "http://ift.tt/1CK6ozv"

    }

    if (segue.identifier == "mensaSegue"){

        DestViewConroller.url = "http://ift.tt/1yrgq1V"

    }

    if (segue.identifier == "absenzenSegue"){

        DestViewConroller.url = "http://ift.tt/1yrgrmm"

    }

    if (segue.identifier == "stundenplanSegue"){

        DestViewConroller.url = "http://ift.tt/1yrgqif"


    }



}

`

Thanks in advance