[logback-dev] [qos-ch/logback] 9ac1e2: Fix NPE when substituting blank variables

[Tony Trinh]

  Branch: refs/heads/master
  Home:   https://github.com/qos-ch/logback
  Commit: 9ac1e28d95eba9dbc51bcd7bcfc8edc6215a2a73
      https://github.com/qos-ch/logback/commit/9ac1e28d95eba9dbc51bcd7bcfc8edc6215a2a73
  Author: Tony Trinh <tony19 at gmail.com>
  Date:   2014-02-06 (Thu, 06 Feb 2014)

  Changed paths:
    M logback-core/src/main/java/ch/qos/logback/core/subst/Parser.java
    M logback-core/src/test/java/ch/qos/logback/core/subst/ParserTest.java
    M logback-core/src/test/java/ch/qos/logback/core/util/OptionHelperTest.java

  Log Message:
  -----------
  Fix NPE when substituting blank variables

The substitution parser attempted to deref a null pointer when a given
variable had a blank value. c.q.l.core.subst.Parser#T() was missing
a null-check.

This was discovered in logback-android's AndroidManifestPropertiesUtil.