Added check for panel's presence. A -> B -> C -> A -> C' C and C' are the same url but look different, maybe because things have been deleted since the C was first shown. Then if go back from C' to A then to C, it will actually go back to C' because the cache holds the latest version of AC. Then going back from C' to B the panels that were there when going from B to C originally might not be there now.
Added check for panel's presence.
A -> B -> C -> A -> C'
C and C' are the same url but look different, maybe because things have been deleted since the C was first shown.
Then if go back from C' to A then to C, it will actually go back to C' because the cache holds the latest version of AC. Then going back from C' to B the panels that were there when going from B to C originally might not be there now.

grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation