[clang-format] Fix a crash with AlignArrayOfStructures option (llvm#86420)

Fixes llvm#86109.

Author: owenca

clang/lib/Format/WhitespaceManager.cpp

@@ -1491,7 +1491,7 @@ WhitespaceManager::CellDescriptions WhitespaceManager::getCells(unsigned Start,
                                                                 : Cell);
         // Go to the next non-comment and ensure there is a break in front
         const auto *NextNonComment = C.Tok->getNextNonComment();
-        while (NextNonComment->is(tok::comma))
+        while (NextNonComment && NextNonComment->is(tok::comma))
           NextNonComment = NextNonComment->getNextNonComment();
         auto j = i;
         while (j < End && Changes[j].Tok != NextNonComment)

clang/unittests/Format/FormatTest.cpp

@@ -21100,7 +21100,14 @@ TEST_F(FormatTest, CatchAlignArrayOfStructuresRightAlignment) {
                 "    [0] = {1, 1},\n"
                 "    [1] { 1, 1, },\n"
                 "    [2] { 1, 1, },\n"
-                "};");
+                "};",
+                Style);
+  verifyNoCrash("test arr[] = {\n"
+                "#define FOO(i) {i, i},\n"
+                "SOME_GENERATOR(FOO)\n"
+                "{2, 2}\n"
+                "};",
+                Style);
 
   verifyFormat("return GradForUnaryCwise(g, {\n"
                "                                {{\"sign\"}, \"Sign\",  "
@@ -21353,7 +21360,14 @@ TEST_F(FormatTest, CatchAlignArrayOfStructuresLeftAlignment) {
                 "    [0] = {1, 1},\n"
                 "    [1] { 1, 1, },\n"
                 "    [2] { 1, 1, },\n"
-                "};");
+                "};",
+                Style);
+  verifyNoCrash("test arr[] = {\n"
+                "#define FOO(i) {i, i},\n"
+                "SOME_GENERATOR(FOO)\n"
+                "{2, 2}\n"
+                "};",
+                Style);
 
   verifyFormat("return GradForUnaryCwise(g, {\n"
                "                                {{\"sign\"}, \"Sign\", {\"x\", "