Bug 36902 [preferences] IllegalArgumentException in JavaEditorHoverConfigurationBlock$3.keyReleased
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/JavaEditorHoverConfigurationBlock.java
int i= fHoverList.getSelectionIndex();
		String modifiers= fModifierEditor.getText();
		fHoverConfigs[i].fModifierString= modifiers;
		fHoverConfigs[i].fStateMask= JavaEditorTextHoverDescriptor.computeStateMask(modifiers);
		if (fHoverConfigs[i].fIsEnabled && fHoverConfigs[i].fStateMask == -1)
			fStatus= new StatusInfo(StatusInfo.ERROR, PreferencesMessages.getFormattedString("JavaEditorHoverConfigurationBlock.modifierIsNotValid", fHoverConfigs[i].fModifierString)); 
		else
			fStatus= new StatusInfo();
		updateStatus();
	}
	private void handleHoverListSelection() {	
		int i= fHoverList.getSelectionIndex();
		boolean enabled= fHoverConfigs[i].fIsEnabled;
		fEnableField.setSelection(enabled);
		fModifierEditor.setEnabled(enabled);
		fModifierEditor.setText(fHoverConfigs[i].fModifierString);
		String description= getContributedHovers()[i].getDescription();
		if (description == null)
			description= ""; 
		fDescription.setText(description);
	}
	private int convertHeightInCharsToPixels(Control control, int chars) {
		GC gc = new GC(control);
		gc.setFont(control.getFont());
		FontMetrics fontMetrics = gc.getFontMetrics();
		gc.dispose();
		if (fontMetrics == null)
			return 0;
		return Dialog.convertHeightInCharsToPixels(fontMetrics, chars);
	}