[LyX/master] Add a risk hedge for timing of initialization

[Koji Yokota]

commit 015d40fb9720447e60ef98d3e39d8a2d4415c45a
Author: Koji Yokota <yokota at lyx.org>
Date:   Sun May 10 22:10:45 2026 +0900

    Add a risk hedge for timing of initialization
---
 src/TextMetrics.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/TextMetrics.cpp b/src/TextMetrics.cpp
index 04827030e5..c7ee6769d5 100644
--- a/src/TextMetrics.cpp
+++ b/src/TextMetrics.cpp
@@ -578,6 +578,10 @@ bool TextMetrics::redoParagraph(pit_type const pit, bool const align_rows)
 	pm.dim().des -= pm.rows().front().ascent();
 
 	// Tell the input method about pm
+	// Note that initial value of im_ is a nullptr, since TextMetrics is
+	// constructed in the initialization of BufferView before GuiInputMethod
+	// is constructed. Don't call this function too early.
+	LBUFERR(im_ != nullptr);
 	im_->setParagraphMetrics(pm);
 
 	changed |= old_dim.height() != pm.dim().height();
@@ -859,6 +863,10 @@ Row TextMetrics::tokenizeParagraph(pit_type const pit) const
 	if (ic_it.inTexted() && ic_it.text() == text_ && ic_it.pit() == pit)
 		ic_pos = ic_it.pos();
 
+	// Note that initial value of im_ is a nullptr, since TextMetrics is
+	// constructed in the initialization of BufferView before GuiInputMethod
+	// is constructed. Don't call this function too early.
+	LBUFERR(im_ != nullptr);
 	docstring & preedit = im_->preeditString();
 
 	// Now we iterate through until we reach the right margin