STEPS TO REPRODUCE 1. go to any URL which have some links, e.g. http://www.mozilla.com/ 2. middle-click a link The bug occurs with "Middle-click opens new tab" preference on. The bug does not occur with "Middle-click opens new tab" preference off or when left-clicking a link. ACTUAL RESULTS WARNING: NS_ENSURE_TRUE(aURI) failed: file nsDefaultURIFixup.cpp, line 75 PLATFORMS AND BUILDS TESTED Bug occurs in SeaMonkey debug build on Linux, about 1 day old. Bug occurs in SeaMonkey debug build on Linux, about 2 weeks old. Bug does not occur in Firefox debug build on Linux, about a week old. (so it seems to me it is a SeaMonkey only problem, but I could be wrong)
looks like tabbedbrowser + favicons
This most likely occurs as a result of bug 113202.
(In reply to comment #4) >This most likely occurs as a result of bug 113202. You're right, I broke the null-check by adding stuff before it.
*** Bug 349990 has been marked as a duplicate of this bug. ***
This particular stack is WFM. Bug 425480 has resulted in a new regression which includes triggering this warning as a side-effect, so I filed bug 482147.