VersionTracker: Ignore libraries without soname

Bug: http://b/20872443
Change-Id: I7bd076885c1feae39af6ea64c9442bcc5ae5a1dc
(cherry picked from commit 8264afb37778bea2a3c6e9aa7144f4877401c3f8)
diff --git a/linker/linker.cpp b/linker/linker.cpp
index fe2c2f0..7d8b266 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -1686,7 +1686,7 @@
     const char* target_soname = si_from->get_string(verneed->vn_file);
     // find it in dependencies
     soinfo* target_si = si_from->get_children().find_if([&](const soinfo* si) {
-      return strcmp(si->get_soname(), target_soname) == 0;
+      return si->get_soname() != nullptr && strcmp(si->get_soname(), target_soname) == 0;
     });
 
     if (target_si == nullptr) {