fix commit "frontend/parse.c, bug fix, PPlex(.."dc1.@m1[vth][1]"..)"

which broke
  let something = foo[var]
notably used in
  examples/Monte_Carlo/MC_ring.sp

src/frontend/parse.c

@@ -680,7 +680,8 @@ PPlex(YYSTYPE *lvalp, struct PPltype *llocp, char **line)
                     atsign = 1;
                 else if (!atsign && *sbuf == '[')
                     break;
-                else if (atsign && *sbuf == ']') {
+                else if (*sbuf == ']') {
+                    if (atsign)
                         sbuf++;
                     break;
                 }

tests/regression/misc/bugs-2.cir

@@ -17,6 +17,9 @@ let gold = 500m
 let bar = foo[2]
 let baz = @v1[dc][2]
 
+let two = 2
+let argh = foo[two]
+
 let fail_count = 0
 
 if bar <> 0.5
@@ -29,6 +32,11 @@ if baz <> 0.5
   let fail_count = fail_count + 1
 end
 
+if argh <> 0.5
+  echo "ERROR: bar = $&argh should be 0.5"
+  let fail_count = fail_count + 1
+end
+
 if fail_count > 0
   echo "ERROR: $&fail_count tests failed"
   quit 1