msvcp90: Fix EOF handling in basic_filebuf<char>::underflow.

dlls/msvcp90/ios.c

diff --git a/dlls/msvcp90/ios.c b/dlls/msvcp90/ios.c
index 8550c6e..9501c8a 100644
--- a/dlls/msvcp90/ios.c
+++ b/dlls/msvcp90/ios.c
@@ -2513,7 +2513,7 @@
         return *basic_streambuf_char_gptr(&this->base);
 
     ret = call_basic_filebuf_char_uflow(this);
-    if(ret)
+    if(ret != EOF)
         ret = call_basic_filebuf_char_pbackfail(this, ret);
     return ret;
 }