updated ErrorDialog messages in case dot.exe path is missing/invalid, if folder location is not configured/invalid in the preferences
diff --git a/eclipse-tools/emf-graphical-viewer/plugins/org.eclipse.app4mc.emf.viewer.plantuml/src/org/eclipse/app4mc/emf/viewer/plantuml/handlers/AbstractPlantUMLHandler.java b/eclipse-tools/emf-graphical-viewer/plugins/org.eclipse.app4mc.emf.viewer.plantuml/src/org/eclipse/app4mc/emf/viewer/plantuml/handlers/AbstractPlantUMLHandler.java
index ef2f034..f9cdff0 100644
--- a/eclipse-tools/emf-graphical-viewer/plugins/org.eclipse.app4mc.emf.viewer.plantuml/src/org/eclipse/app4mc/emf/viewer/plantuml/handlers/AbstractPlantUMLHandler.java
+++ b/eclipse-tools/emf-graphical-viewer/plugins/org.eclipse.app4mc.emf.viewer.plantuml/src/org/eclipse/app4mc/emf/viewer/plantuml/handlers/AbstractPlantUMLHandler.java
@@ -95,7 +95,10 @@
 				
 				String genFolder = DiagramCreator.getGenFolder(genFolderPath, eObject != null ? eObject.eResource() : null);
 				if (genFolder == null || genFolder.length() == 0) {
-					openErrorDialog(shell, "Folder for diagram generation is not set. Configure a folder in Preferences -> AMALTHEA Graphical Representation");
+					openErrorDialog(shell, "Folder for diagram generation is not set. Configure a folder path in Preferences -> AMALTHEA Graphical Representation");
+					return;
+				}else if(!new File(genFolder).exists()) {
+					openErrorDialog(shell, "Invalid folder path is specified. Configure a valid folder path in Preferences -> AMALTHEA Graphical Representation");
 					return;
 				}
 				
@@ -130,10 +133,10 @@
 	
 	protected boolean verifyDotPath(Shell shell, String dotPath) {
 		if (dotPath == null) {
-			openErrorDialog(shell, "DOT file exe path is not set in the Preferences");
+			openErrorDialog(shell, "Missing Graphviz DOT.exe location in Preferences."+System.getProperty("line.separator")+"Please specify location via \"Window - Preferences - Plantuml - Path\" to the dot.exe file of Graphviz.");
 			return false;
 		} else if (!new File(dotPath).exists()) {
-			openErrorDialog(shell, "DOT file exe is not existing in the specified path. Update the valid path in Preferences -> AMALTHEA Graphical Representation node");
+			openErrorDialog(shell, "Invalid path of Graphviz DOT.exe is present in Preferences."+System.getProperty("line.separator")+"Please specify valid path via \"Window - Preferences - Plantuml - Path\" to the dot.exe file of Graphviz.");
 			return false;
 		}