Engine: Fix edge case where OSD_Printf() may wrongly remove the last char in a string

source/build/src/osd.cpp

@@ -1686,11 +1686,9 @@ int OSD_Printf(const char *f, ...)
         va_list va;
         buf = (char *)Xrealloc(buf, (size <<= 1));
         va_start(va, f);
-        len = Bvsnprintf(buf, size-1, f, va);
+        len = Bvsnprintf(buf, size, f, va);
         va_end(va);
-    } while ((unsigned)len > size-1);
-    
-    buf[len] = 0;
+    } while ((unsigned)len >= size);
 
     OSD_Puts(buf);