Remove extraneous spaces and add $(NULL) to XPIDLSRCS.

xpcom/proxy/tests/Makefile.in

@@ -50,14 +50,15 @@ CPPSRCS		= proxytests.cpp \
 		proxy-create-threadsafety.cpp \
 		$(NULL)
 
-CPP_UNIT_TESTS += \ 
+CPP_UNIT_TESTS += \
   proxytests.cpp \
   proxy-create-threadsafety.cpp \
   $(NULL)
 
-XPIDLSRCS  = \ 
+XPIDLSRCS  = \
   nsITestProxy.idl \
-  nsITestProxyOrig.idl
+  nsITestProxyOrig.idl \
+  $(NULL)
 
 SIMPLE_PROGRAMS	= $(CPPSRCS:.cpp=$(BIN_SUFFIX))