Don't use invalid iterator in Fallback-Of handling

cppcheck reports: (error) Iterator 't' used after element has been erased.

The loop is actually fashioned to deal with this (not in the most
efficient way, but in simplest and speed isn't really a concern here)
IF this codepath had a "break" at the end… so I added one.

Note that the tests aren't failing before (and hopefully after) the
change as the undefined behavior we encounter is too stable.

Thanks: David Binderman for reporting

1 files changed, 1 insertions, 0 deletions

diff --git a/apt-pkg/deb/debmetaindex.cc b/apt-pkg/deb/debmetaindex.cc
index 6cbed85a7..9c7c70784 100644
--- a/apt-pkg/deb/debmetaindex.cc
+++ b/apt-pkg/deb/debmetaindex.cc
@@ -1043,6 +1043,7 @@ class APT_HIDDEN debSLTypeDebian : public pkgSourceList::Type		/*{{{*/
 	    auto const tv = *t;
 	    mytargets.erase(t);
 	    mytargets.emplace_back(tv);
+	    break;
 	 }
 	 if (Changed == false)
 	    break;