inetcomm: Sign-compare warning fix

[Andrew Talbot]

Changelog:
    inetcomm: Sign-compare warning fix.

diff --git a/dlls/inetcomm/mimeole.c b/dlls/inetcomm/mimeole.c
index 7e9d709..03b97a3 100644
--- a/dlls/inetcomm/mimeole.c
+++ b/dlls/inetcomm/mimeole.c
@@ -1229,8 +1229,10 @@ static HRESULT WINAPI sub_stream_Seek(
         return STG_E_INVALIDFUNCTION;
     }
 
-    if(new_pos.QuadPart < 0) new_pos.QuadPart = 0;
-    else if(new_pos.QuadPart > This->length.QuadPart) new_pos.QuadPart = This->length.QuadPart;
+    if(new_pos.QuadPart < 0)
+        new_pos.QuadPart = 0;
+    else if((ULONGLONG)new_pos.QuadPart > This->length.QuadPart)
+        new_pos.QuadPart = This->length.QuadPart;
 
     This->pos.QuadPart = new_pos.QuadPart;