vfs,avfs: verify an interpreter was found on #! line

. if not, NULL *interp is dereferenced

test/run

@@ -16,7 +16,7 @@ tests="   1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 \
          41 42 43 44 45 45-gcc 46 47 48 49 49-gcc 50 \
          51 51-gcc 52 52-gcc 53 54 55 56 57 58 59\
          60 61 \
-	 sh1.sh sh2.sh"
+	 sh1.sh sh2.sh interp.sh"
 tests_no=`expr 0`
 
 # Directory must be owned by bin

test/testinterp.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+
+# See if the system can handle an unexpected whitespace-only interpreter line
+
+echo -n "Test interpreter "
+
+set -e
+TMPSH=tst$$.sh
+rm -f $TMPSH
+echo '#!   ' >$TMPSH
+chmod 755 $TMPSH
+./$TMPSH || true
+rm -f $TMPSH
+echo "ok"