Hi Here is a Fix

Symptom: Charts disply no graphs, only the chart dashlet header.
BACKGROUND: (Skip further down if you just want the answer)
Check of log (sugarcrm.log) shows and error like
[FATAL] Unable to return chart data, invalid xml for file cache/xml/cf5c5670-6587-c96c-ad17-5488356b7436_11239fac-ffe5-8e9b-1016-5492ec21299f.xml
WHAT HAPPENED
For PHP 5.5.1+ the PCRE Extension has been updated, incoporating a change to the Regex handler.
http://php.net/manual/en/pcre.installation.php
PCRE Changelog for this version:
http://www.pcre.org/changelog.txt
This means that the jsChart.php fails with this error in the Apache error.log
preg_replace(): Compilation failed: invalid range in character class at offset 36
HOTFIX
You can correct this problem by amending line 719 in ./include/SugarCharts/jsChart.php
replace
$pattern[] = ā/<link>([a-zA-Z0-9#?&%.;[]/=+_-\s]+)</link>/eā;
with
$pattern[] = ā/<link>([a-zA-Z0-9#?&%.;[]/=+\s-_]+)</link>/eā;
Thanks to pabloarias and his post here
https://community.sugarcrm.com/sugarcrm/topics/warning-preg-replace-compilation-failed-invalid-range-in-character-class-at-offset-36-in-sugarcharts-jschart-php-on-line-719
Or if you prefer you can simply swap the jsCharts.php file in for this one attached, remove the .txt extension so you have jsChart.php
FOR DEVELOPMENT
I will push this fix to my branch on Git Hub, and send in a Pull Request so that this fix can become upgrade safe.