fix bug in MedicalImageProperties

An iterator returned from a container .find(...)
was being dereferenced without checking for a
returned end of container failure case.  The
fix checks for end of container condition before
derefencing the iterator.

Change-Id: Iccc5a31629d09a143e3712ba9c936528ef868afc
Merge topic 'med-image-props-fix' into master

9aadfc9f fix bug in MedicalImageProperties