[processing] fixed otb version detection when no otb path is defined or found

Author: volaya

python/plugins/processing/algs/otb/OTBUtils.py

@@ -135,6 +135,9 @@ def getInstalledVersion(runOtb=False):
     if _installedVersionFound and not runOtb:
         return _installedVersion
 
+    if otbPath() is None:
+        _installedVersionFound = False
+        return None
     commands = [os.path.join(otbPath(), "otbcli_Smoothing")]
     progress = SilentProgress()
     out = executeOtb(commands, progress, False)