NavigateToDefinitionHandler doesn't check null which will cause NullPointerException

[Poytr1]

This issue is related to: #879
https://github.com/eclipse/eclipse.jdt.ls/blob/ca81aa7b935b52c0aff7624fa9f330c832578233/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/handlers/NavigateToDefinitionHandler.java#L79
The location here may be null, and if it is, a NullPointerException will be thrown which isn't caught as well.

The interesting thing is that when I goto definition on java.lang.string in macOS, this exception doesn't occur while it occurs on Linux. Not sure if it has anything to do with the if logic above.

Following is the stack trace(caught):

java.lang.NullPointerException
        at org.eclipse.jdt.ls.core.internal.handlers.NavigateToDefinitionHandler.fixLocation(NavigateToDefinitionHandler.java:79)
        at org.eclipse.jdt.ls.core.internal.handlers.NavigateToDefinitionHandler.computeDefinitionNavigation(NavigateToDefinitionHandler.java:62)
        at org.eclipse.jdt.ls.core.internal.handlers.NavigateToDefinitionHandler.definition(NavigateToDefinitionHandler.java:45)
...

[yaohaizh]

@Poytr1 Would you open a PR for this issue?

[Poytr1]

@Poytr1 Would you open a PR for this issue?

Sure