ed: Don't clear modflag until is safe

Setting modflag unconditionally in the E command could
produce that after an error happening dealing with the E
command then unsaved files were silently ignored.

ed.c

@@ -1448,17 +1448,17 @@ repeat:
 		chkprint(0);
 		break;
 	case 'E':
-		modflag = 0;
 	case 'e':
 		ensureblank();
 		if (nlines > 0)
 			goto unexpected;
-		if (modflag)
+		if (cmd == 'e' && modflag)
 			goto modified;
 		setscratch();
 		deflines(curln, curln);
 		doread(getfname(cmd));
 		clearundo();
+		modflag = 0;
 		break;
 	default:
 		error("unknown command");

tests/0015-ed.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+../ed -s /dev/null <<EOF | grep 'file modified' > /dev/null
+a
+1
+2
+.
+1E
+q
+h
+q
+EOF