gdi32: Prevent possible buffer overrun.

dlls/gdi32/font.c

diff --git a/dlls/gdi32/font.c b/dlls/gdi32/font.c
index c81a9c82..ed64166 100644
--- a/dlls/gdi32/font.c
+++ b/dlls/gdi32/font.c
@@ -2596,13 +2596,13 @@
     int index = 0;
     switch (flags) {
     case TCI_SRCFONTSIG:
-	while (!(*lpSrc>>index & 0x0001) && index<MAXTCIINDEX) index++;
+      while (index < MAXTCIINDEX && !(*lpSrc>>index & 0x0001)) index++;
       break;
     case TCI_SRCCODEPAGE:
-      while (PtrToUlong(lpSrc) != FONT_tci[index].ciACP && index < MAXTCIINDEX) index++;
+      while (index < MAXTCIINDEX && PtrToUlong(lpSrc) != FONT_tci[index].ciACP) index++;
       break;
     case TCI_SRCCHARSET:
-      while (PtrToUlong(lpSrc) != FONT_tci[index].ciCharset && index < MAXTCIINDEX) index++;
+      while (index < MAXTCIINDEX && PtrToUlong(lpSrc) != FONT_tci[index].ciCharset) index++;
       break;
     default:
       return FALSE;