fix: fix crash when fontconfig fallback pattern has no charset

debian/changelog

@@ -1,3 +1,9 @@
+qt6-base (6.8.0+dfsg-0deepin37) unstable; urgency=medium
+
+  * Fix crash when fontconfig fallback pattern has no charset.
+
+ -- zhanghongyuan <zhanghongyuan@uniontech.com>  Mon, 28 Sep 2026 09:27:41 +0800
+
 qt6-base (6.8.0+dfsg-0deepin36) unstable; urgency=medium
 
   * fix: enable fix-ComboBox-Wheelevent.patch in the patch series so

debian/patches/Fix-crash-when-fontconfig-fallback-pattern-has-no-charset.patch

@@ -0,0 +1,26 @@
+Author: zhanghongyuan<zhanghongyuan@uniontech.com>
+Date:   Mon, 28 Sep 2026 09:59:10 +0800
+Subject: Fix-crash-when-fontconfig-fallback-pattern-has-no-charset
+Upstream: https://codereview.qt-project.org/c/qt/qtbase/+/750214
+
+---
+
+Index: qt6-base/src/gui/text/unix/qfontenginemultifontconfig.cpp
+===================================================================
+--- qt6-base.orig/src/gui/text/unix/qfontenginemultifontconfig.cpp
++++ qt6-base/src/gui/text/unix/qfontenginemultifontconfig.cpp
+@@ -25,9 +25,11 @@ bool QFontEngineMultiFontConfig::shouldL
+     bool charSetHasChar = true;
+     FcPattern *matchPattern = getMatchPatternForFallback(at - 1);
+     if (matchPattern != nullptr) {
+-        FcCharSet *charSet;
+-        FcPatternGetCharSet(matchPattern, FC_CHARSET, 0, &charSet);
+-        charSetHasChar = FcCharSetHasChar(charSet, ucs4);
++        FcCharSet *charSet = nullptr;
++        if (FcPatternGetCharSet(matchPattern, FC_CHARSET, 0, &charSet) == FcResultMatch
++            && charSet != nullptr) {
++            charSetHasChar = FcCharSetHasChar(charSet, ucs4);
++        }
+     }
+
+     return charSetHasChar;

debian/patches/series

@@ -59,3 +59,4 @@ CVE-2026-19248_fix-unbounded-nesting-depth-in-QDomNode-dtor.patch
 CVE-2026-78253_fix-stack-exhaustion-in-readElementText.patch
 CVE-2026-82292_guard-against-null-nodes-in-QDomBuilder.patch
 fix-ComboBox-Wheelevent.patch
+Fix-crash-when-fontconfig-fallback-pattern-has-no-charset.patch