Be careful before using buffer parameters in colAlign

Make InsetGrid::colAlign a normal method and make it check whether
buffer is valid before using it. This avoids crashes as we have seen
in 2.3.3 (see e.g. #11686).

There is still an assertion so that failure is noticeable before release.

src/mathed/InsetMathGrid.cpp

@@ -1831,8 +1831,7 @@ bool InsetMathGrid::getStatus(Cursor & cur, FuncRequest const & cmd,
 }
 
 
-// static
+char InsetMathGrid::colAlign(HullType type, col_type col) const
-char InsetMathGrid::colAlign(HullType type, col_type col, BufferParams const & bp)
 {
 	switch (type) {
 	case hullEqnArray:
@@ -1841,10 +1840,13 @@ char InsetMathGrid::colAlign(HullType type, col_type col, BufferParams const & b
 	case hullMultline:
 		return 'c';
 	case hullGather:
-		if (!bp.is_math_indent)
+		LASSERT(isBufferValid(),
-			return 'c';
+				LYXERR0("Buffer not set correctly. Please report!");
-		else
+				return 'c';);
+		if (buffer().params().is_math_indent)
 			return 'l';
+		else
+			return 'c';
 
 	case hullAlign:
 	case hullAlignAt:

src/mathed/InsetMathGrid.h

@@ -272,7 +272,7 @@ protected:
 	// InsetMathSplit.
 	/// The value of a fixed col align for a certain hull type (can
 	/// depend on the "indent math" setting).
-	static char colAlign(HullType type, col_type col,  BufferParams const &);
+	char colAlign(HullType type, col_type col) const;
 	/// The value of a fixed col spacing for a certain hull type
 	static int colSpace(HullType type, col_type col);
 

src/mathed/InsetMathHull.cpp

@@ -430,7 +430,7 @@ InsetMath::mode_type InsetMathHull::currentMode() const
 // alignment is not implemented in the LyXHTML output.
 char InsetMathHull::defaultColAlign(col_type col)
 {
-	return colAlign(type_, col, buffer().params());
+	return colAlign(type_, col);
 }
 
 
@@ -452,7 +452,7 @@ char InsetMathHull::displayColAlign(idx_type idx) const
 	case hullXAlignAt:
 	case hullXXAlignAt:
 	case hullFlAlign:
-		return colAlign(type_, col(idx), buffer().params());
+		return colAlign(type_, col(idx));
 	default:
 		break;
 	}

src/mathed/InsetMathSplit.cpp

@@ -62,7 +62,7 @@ char InsetMathSplit::defaultColAlign(col_type col)
 	    || name_ == "aligned"
 	    || name_ == "align"
 	    || name_ == "alignedat")
-		return colAlign(hullAlign, col, buffer().params());
+		return colAlign(hullAlign, col);
 	return 'l';
 }
 
@@ -79,7 +79,7 @@ char InsetMathSplit::displayColAlign(idx_type idx) const
 	    || name_ == "aligned"
 	    || name_ == "align"
 	    || name_ == "alignedat")
-		return colAlign(hullAlign, col(idx), buffer().params());
+		return colAlign(hullAlign, col(idx));
 	return InsetMathGrid::displayColAlign(idx);
 }