[LyX/master] Revert "Fix crash when dissolving a top level math inset"

[Jean-Marc Lasgouttes]

commit 62d61e765582f6fa297d933282938b127bf47f04
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Sun Jul 23 00:22:22 2023 +0200

    Revert "Fix crash when dissolving a top level math inset"
    
    The code was too convoluted and actually wrong (the -1 should have been -2).
    
    This reverts commit c75522bbb7a0044f2370ced294a27738d47935ea.
---
 src/mathed/InsetMathNest.cpp |   18 ++++++------------
 1 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/src/mathed/InsetMathNest.cpp b/src/mathed/InsetMathNest.cpp
index a780a95..804ee4d 100644
--- a/src/mathed/InsetMathNest.cpp
+++ b/src/mathed/InsetMathNest.cpp
@@ -1284,16 +1284,13 @@ void InsetMathNest::doDispatch(Cursor & cur, FuncRequest & cmd)
 			cur.undispatched();
 		break;
 	}
-	case LFUN_INSET_DISSOLVE: {
-		bool const enabled = cur.inMathed()
-			&& (&cur.inset() != this || cur[cur.depth() - 1].inset().inMathed());
-		if (enabled) {
+	case LFUN_INSET_DISSOLVE:
+		if (!asHullInset()) {
 			cur.recordUndoInset();
-			// FIXME: this loses data
 			cur.pullArg();
 		}
 		break;
-	}
+
 	case LFUN_MATH_LIMITS: {
 		InsetMath * in = 0;
 		if (cur.pos() < cur.lastpos() && cur.nextMath().allowsLimitsChange())
@@ -1530,13 +1527,10 @@ bool InsetMathNest::getStatus(Cursor & cur, FuncRequest const & cmd,
 		break;
 	}
 
-	case LFUN_INSET_DISSOLVE: {
-		// Do not dissolve a math inset which is in text
-		bool const enabled = cur.inMathed()
-			&& (&cur.inset() != this || cur[cur.depth() - 1].inset().inMathed());
-		flag.setEnabled(enabled);
+	case LFUN_INSET_DISSOLVE:
+		flag.setEnabled(!asHullInset());
 		break;
-	}
+
 	case LFUN_PASTE: {
 		docstring const & name = cmd.argument();
 		if (name == "html" || name == "latex")