EnvInjectVariableGetter: Avoid NPE when node is null

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Avoid NPEs in property file variables injection when workspace is null

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Annotate methods, which may return nulls

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Merge pull request #32 from synopsys-arc-oss/NPE_checks

Prevent NPEs in the code