bug 899849 - fix MozbuildObject.from_environment to work right when no mozconfig specified. r=gps

python/mozbuild/mozbuild/base.py

@@ -135,7 +135,6 @@ class MozbuildObject(ProcessExecutionMixin):
                 topsrcdir = dir_path
                 break
 
-        if not topsrcdir:
         # See if we're running from a Python virtualenv that's inside an objdir.
         mozinfo_path = os.path.join(os.path.dirname(sys.prefix), "mozinfo.json")
         if os.path.isfile(mozinfo_path):