Fix wxGrid test crash and add debug build support

The wxGrid test was crashing with "memory access out of bounds" due to
an initialization order bug in grid_test.cpp: during CreateGrid(), wxGrid
fires cell selection events which triggered the OnGridCellSelect handler
that called m_log->AppendText() before m_log was initialized.

Fix: Add null check in LogEvent() to guard against events firing before
m_log is created.

Also adds --debug flag to build-wasm-test.sh for debugging WASM crashes:
- Builds with DWARF symbols (-g) and source maps (-gsource-map)
- No optimization (-O0) preserves debugging context
- Stack traces show actual function names instead of wasm-function[N]

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/build-wasm-test.sh

@@ -1,9 +1,20 @@
 #!/bin/bash
 # Build the wxWidgets WASM test applications
 # This script creates library symlinks and builds the test apps
+#
+# Usage:
+#   ./build-wasm-test.sh          # Normal optimized build
+#   ./build-wasm-test.sh --debug  # Debug build with DWARF symbols and source maps
 
 set -e
 
+DEBUG_BUILD=0
+for arg in "$@"; do
+    if [ "$arg" = "--debug" ]; then
+        DEBUG_BUILD=1
+    fi
+done
+
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 PROJECT_ROOT="$(dirname "$SCRIPT_DIR")"
 BUILD_DIR="$PROJECT_ROOT/build-wasm/wxwidgets-universal"
@@ -12,6 +23,11 @@ WASM_APP_DIR="$TESTS_DIR/wasm-app"
 STANDALONE_DIR="$WASM_APP_DIR/standalone"
 
 echo "=== Building wxWidgets WASM Test Applications ==="
+if [ "$DEBUG_BUILD" = "1" ]; then
+    echo "Mode: DEBUG (with DWARF symbols and source maps)"
+else
+    echo "Mode: Release (optimized)"
+fi
 echo "Project root: $PROJECT_ROOT"
 echo "wxWidgets build: $BUILD_DIR"
 echo "Test app dir: $WASM_APP_DIR"
@@ -45,8 +61,13 @@ cd "$WASM_APP_DIR"
 # Clean any previous build
 make -f Makefile.wasm clean 2>/dev/null || true
 
-# Build all
-make -f Makefile.wasm
+# Build all (pass DEBUG flag if requested)
+if [ "$DEBUG_BUILD" = "1" ]; then
+    # Debug build: -g for DWARF, -gsource-map for source maps, -O0 for no optimization
+    make -f Makefile.wasm DEBUG=1
+else
+    make -f Makefile.wasm
+fi
 
 echo ""
 echo "=== Build complete ==="