proc/variables: crash while reading unintialized variable

Fixes #384

proc/variables.go

@@ -3,6 +3,7 @@ package proc
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"go/constant"
 	"go/parser"
@@ -927,6 +928,10 @@ func (v *Variable) loadArrayValues(recurseLevel int) {
 	if v.Unreadable != nil {
 		return
 	}
+	if v.Len < 0 {
+		v.Unreadable = errors.New("Negative array length")
+		return
+	}
 
 	count := v.Len
 	// Cap number of elements